how to write abstract literature review

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Writing Abstracts for a Literature Review in APA Format

Do you need to know how to write a literature review abstract in APA? You’ve come to the right place. This citation example focuses on abstract writing in an APA format style paper. Learning how to write an abstract in APA is an excellent skill to have, as it helps you develop the ability to summarize the essential points in your paper. In addition to a how-to, you can explore several APA abstract examples including a literature review abstract example.

Types of Research Papers

You may be asked to prepare various kinds of research papers as a student, including:

• Empirical study
• Theory-oriented
• Methodological

A literature review paper is one you’ll be asked to write frequently, as many times, there is not enough time in a class setting to complete extensive research. Therefore, it’s important to know how to create an abstract for your literature review.

What Is an Abstract?

An abstract is a concise summary of the purpose or aim of your research in your APA paper. You’ve probably seen an abstract a time or two when looking at a scholarly journal. These examples of abstracts in APA tell you whether the piece is worth your time to read. Abstracts vary by type but should include:

• research questions, problems, and/or a hypothesis
• research methods
• study results and conclusions
• Recommendations and implications
• critical points of a literature review

The official writing style of the American Psychological Association , APA format is designed for psychology and social science papers. Therefore, abstracts you create in this writing style are for this purpose. Additionally, per the 7th edition of APA writing style, abstracts and keywords are no longer required for student papers, unless required by your teacher. 

Abstract Word Limits

The maximum word count for an APA abstract is 250 words. However, your instructor may ask for fewer words or provide you with additional guidance. Some instructors or publications may restrict the word count to 150.

How to Write an Abstract in APA

Since the abstract is a concise summary of your paper, you write it after you have finished your paper. Therefore, you have a clear idea of what to include in this short paragraph. Now, let’s explore the details of how to write and format an abstract for your APA paper.

APA Abstract Format

The abstract page is the second page of your report, right after the title page. This page is numbered 2 on your report.

• On the first line of the page, center the word Abstract in bold. (Do not underline, italicize, or otherwise format the title.)
• On the second line, start your abstract. (Do not indent.)
• Use a readable font like Times New Roman 12-point or Calibri 11-point.
• Write the abstract as a single paragraph.
• Double-space, 1-inch margins on all sides.

Inserting Keywords into an APA Abstract

In today’s digital world, it is vital to think about ways readers can find your work online. Adding  keywords at the end of your abstract guides online searches. These keywords need to accurately represent the paper and be specific.

After the abstract paragraph, type Keywords:  italicized and indented.

Keywords:  digital print, online sources

Abstract Example in APA

This article is an examination of the history of gender demographics in the field of librarianship. The historical development and subsequent “feminization” of librarianship continues to influence the gender wage gap and the disproportionate leadership bias in the field today. This article examines the stereotyping of librarians and the cyclical effect of genderizing the profession. Consideration of current trends and data in librarian demographics demonstrates a consistent decrease in gender diversity, accompanied by a troubling lack of women leaders and executives. Additionally, this article explores options for combating the gender perceptions that negatively impact women in the library and information science fields, including management and negotiation training in graduate programs, increased emphasis on technological skills, and professional organization advocacy.

Keywords : gender, demographics, stereotyping, librarians

How to Write an Abstract for a Literature Review

When writing an abstract for a literature review, you take the same basic approach as you do for a general abstract. However, since you are reviewing other literature on a topic, you have some unique elements, including:

• First, briefly state the research topic  and questions.
• Then, using the primary studies in the literature you reviewed, include the participants in the studies and the main results.
• Remember to include the conclusion of your literature review.
• Finally, finish with a sentence about any implications or future research that developed from the research presented in your paper.

Literature Review Abstract Example With Keywords

The future of books and libraries is put into question by the increasing popularity of e-books and the use of computers as text platforms. To anticipate which reading platform—print, e-readers, or computer displays—will dominate in the coming years, recent research and experimental data on the suitability of each reading platform for reading comprehension will be considered, from the perspectives of optical issues, cognition, and metacognition. It will be shown that, while printed books are most conducive to learning from longer, more challenging texts, e-readers and computer displays offer convenience and some distinct advantages to readers in particular situations. This synthesis of current research will be helpful to librarians working in digital and print book purchasing and collection development, as well as those making long-range planning decisions.

Keywords : books, digital books, e-paper, reading comprehension, cognition

Tips for Writing a Literature Review Abstract in APA

Abstracts can be challenging, especially if you are new to the abstract writing game. Get some quick tips to make abstract writing easy.

• Create a rough draft. This ensures you say everything you need to and the fluff can be edited out.
• Check out professional abstracts.
• Get feedback on your abstract.
• Keep it concise. In an abstract, staying in your word count is essential.

Sectioning Your APA Research Paper

In the seventh edition of APA style , a research paper has four sections:

A Crucial Element

Knowing how to write an abstract in APA is a critical part of your school research paper. Thus, you should put a lot of thought into creating your APA abstract and make sure it includes all the required elements. As always, be sure to follow your teacher’s guidance for the length and format of your APA paper and abstract.

Annotated Bibliography Examples

Understanding APA Literature Reviews

FAQ Writing Abstracts for a Literature Review in APA Format

What is an apa abstract example.

An example of an abstract can be found on the second page of an APA paper. The abstract provides a brief break down of the article to help readers to understand how the paper is useful to their research. An abstract example includes a page number, title (Abstract), abstract text, and keywords at the bottom.

How do you write an abstract?

To write an abstract in APA, you want to include the research questions, research methods, types of research included, conclusions, and implications of the research. The abstract is going to be less than 250 words; therefore, it needs to be concise and to the point. To make sure your abstract is concise, you can create a rough draft and edit it down.

How do you write an abstract for APA 7th edition?

To write an abstract in APA 7th edition, you need to include the page number, title abstract in bold, abstract text of fewer than 250 words, and keywords. The abstract text should provide a concise overview of your APA paper, including research questions, hypotheses, study results, and conclusions. Additionally, APA 7 edition student papers do not require an abstract.

What makes a good abstract?

A good abstract in APA is a clear, concise overview of your research paper. It includes the research topic and questions, studies reviewed, conclusions, implications, and research methods. It's less than 250 words and includes keywords at the end.

What are keywords in APA format?

The keywords in an APA format abstract make the abstract easy to search in online databases. Additionally, they provide readers with a quick idea of the general topics covered in the paper. APA abstract keywords are found at the bottom of the paper, and the word "keywords" is indented and in italics.

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Putting APA References in Alphabetical Order

Apa citation newspaper article examples, apa style citations for quotes, paraphrasing, and references, 8 apa book reference examples.

How to Write a Literature Review

• Critical analysis
• Sample Literature Reviews
• Scaffold examples for organising Literature Reviews
• Writing an Abstract
• Creating Appendices
• APA Reference Guide
• Library Resources
• Guide References

What is an abstract?

What is an Abstract?

An abstract is a short summary of an article, essay or research findings. A well-written abstract will provide the reader with a brief overview of the entire article, including the article's purpose, methodology and conclusion. An abstract should give the reader enough detail to determine if the information in the article meets their research needs...and it should make them want to read more!

While an abstract is usually anywhere between 150 - 300 words, it is important to always establish with your teacher the desired length of the abstract you are submitting.

This excellent guide from the University of Melbourne is a great snapshot of how to write an abstract.

Here are a few links to some useful abstract examples:

University of New South Wales

University of Wollongong

Michigan State University

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• Next: Creating Appendices >>
• Last Updated: Apr 8, 2024 9:14 AM
• URL: https://saintpatricks-nsw.libguides.com/lit_review

How To Write An Abstract For A Literature Review Effectively

Master the art of how to write an abstract for a literature review with this informative guide. Start creating standout abstracts today!

Table of Contents

What Is An Abstract In Literature Review

Purpose of an abstract in a literature review, consider the audience for your abstract, guidelines for writing an abstract for a literature review, general information in an abstract for a literature review, related reading, what are the 5 parts of an abstract, 1. introduction, 5. conclusion, enhanced reading and writing with unriddle's ai-powered tools, how to write an abstract for a literature review, briefly state the research topic and questions, include the participants and main results, conclude the abstract with the conclusion of your literature review, mention implications or future research, complete step-by-step guide on how to use unriddle's ai research tool, interact with documents, automatic relations, citing your sources, writing with ai, chat settings, examples of high-quality abstracts, conclusions, more examples of abstracts for literature reviews, abstract checklist for writing a good review paper, background: setting the stage for your work, aim: what goals do you intend to achieve what gap are you filling, approach: a summary of your methods, results: what are the main findings of your study, conclusions: what are the main conclusions of your research, writing guidelines, read faster & write better with unriddle for free today, ai assistant for efficient research, citation management and text generation, collaborative workspace for enhanced productivity.

• Systematic Literature Review
• Systematic Review Vs Literature Review
• Literature Review Generator
• Thematic Literature Review
• How To Write A Literature Review
• Literature Review Outline Example
• Literature Review Example

• This part points to the applications or wider implications and interpretation scope of the work done.
• It tells the reader the benefits of the findings and how they can be applied.
• It helps the reader to understand the relevance of the paper to their lives, knowledge, and practices.
• This section is crucial to a literature review abstract.
• It is an essential aspect of the abstract and must be clearly stated.
• Unriddle is trusted by thousands of researchers and students, from the classroom to the boardroom.
• Unriddle generates an AI assistant on top of any document so you can quickly find, summarize and understand info. No more endless skimming.
• Unriddle understands the meaning behind your writing and automatically links you to relevant things you’ve read and written about in the past.
• Highlight text and Unriddle will show you the most relevant sources from your library using AI. Never lose a citation again.
• Generate text with AI autocomplete to improve and expand your writing, with all suggestions based on the context of what you're working on.

• Interact with documents via AI so you can quickly find and understand info.
• Then start writing in a new Note and Unriddle will show you relevant content from your library as you type.
• Get started by uploading a document .
• Or read on for the full rundown.

• Model: the machine learning model used to generate responses.
• Temperature: the amount of creative license you give to the AI.
• Max length: the maximum number of words generated in a response.

• Google Scholar Alternative
• Narrative Literature Review
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• Your abstract should be concise, at most 200 words, and focused.
• The abstract should be written for the audience of this journal: do not assume too much or too little background with the topic.
• Ensure that all of the information found in the abstract also can be found in the body of the paper.
• Ensure that the important information of the paper is found in the abstract.
• Avoid: using the first paragraph of the introduction as an abstract; citations in the abstract; acronyms (but if used, spell them out); referring to figures or tables from the body of the paper; use of the first person; use of words like “new” or “novel,” or phrases like “in this paper,” “we report,” or “will be discussed.”
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• How To Do A Systematic Literature Review
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Writing a Literature Review

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A literature review is a document or section of a document that collects key sources on a topic and discusses those sources in conversation with each other (also called synthesis ). The lit review is an important genre in many disciplines, not just literature (i.e., the study of works of literature such as novels and plays). When we say “literature review” or refer to “the literature,” we are talking about the research ( scholarship ) in a given field. You will often see the terms “the research,” “the scholarship,” and “the literature” used mostly interchangeably.

Where, when, and why would I write a lit review?

There are a number of different situations where you might write a literature review, each with slightly different expectations; different disciplines, too, have field-specific expectations for what a literature review is and does. For instance, in the humanities, authors might include more overt argumentation and interpretation of source material in their literature reviews, whereas in the sciences, authors are more likely to report study designs and results in their literature reviews; these differences reflect these disciplines’ purposes and conventions in scholarship. You should always look at examples from your own discipline and talk to professors or mentors in your field to be sure you understand your discipline’s conventions, for literature reviews as well as for any other genre.

A literature review can be a part of a research paper or scholarly article, usually falling after the introduction and before the research methods sections. In these cases, the lit review just needs to cover scholarship that is important to the issue you are writing about; sometimes it will also cover key sources that informed your research methodology.

Lit reviews can also be standalone pieces, either as assignments in a class or as publications. In a class, a lit review may be assigned to help students familiarize themselves with a topic and with scholarship in their field, get an idea of the other researchers working on the topic they’re interested in, find gaps in existing research in order to propose new projects, and/or develop a theoretical framework and methodology for later research. As a publication, a lit review usually is meant to help make other scholars’ lives easier by collecting and summarizing, synthesizing, and analyzing existing research on a topic. This can be especially helpful for students or scholars getting into a new research area, or for directing an entire community of scholars toward questions that have not yet been answered.

What are the parts of a lit review?

Most lit reviews use a basic introduction-body-conclusion structure; if your lit review is part of a larger paper, the introduction and conclusion pieces may be just a few sentences while you focus most of your attention on the body. If your lit review is a standalone piece, the introduction and conclusion take up more space and give you a place to discuss your goals, research methods, and conclusions separately from where you discuss the literature itself.

Introduction:

• An introductory paragraph that explains what your working topic and thesis is
• A forecast of key topics or texts that will appear in the review
• Potentially, a description of how you found sources and how you analyzed them for inclusion and discussion in the review (more often found in published, standalone literature reviews than in lit review sections in an article or research paper)
• Summarize and synthesize: Give an overview of the main points of each source and combine them into a coherent whole
• Analyze and interpret: Don’t just paraphrase other researchers – add your own interpretations where possible, discussing the significance of findings in relation to the literature as a whole
• Critically Evaluate: Mention the strengths and weaknesses of your sources
• Write in well-structured paragraphs: Use transition words and topic sentence to draw connections, comparisons, and contrasts.

Conclusion:

• Summarize the key findings you have taken from the literature and emphasize their significance
• Connect it back to your primary research question

How should I organize my lit review?

Lit reviews can take many different organizational patterns depending on what you are trying to accomplish with the review. Here are some examples:

• Chronological : The simplest approach is to trace the development of the topic over time, which helps familiarize the audience with the topic (for instance if you are introducing something that is not commonly known in your field). If you choose this strategy, be careful to avoid simply listing and summarizing sources in order. Try to analyze the patterns, turning points, and key debates that have shaped the direction of the field. Give your interpretation of how and why certain developments occurred (as mentioned previously, this may not be appropriate in your discipline — check with a teacher or mentor if you’re unsure).
• Thematic : If you have found some recurring central themes that you will continue working with throughout your piece, you can organize your literature review into subsections that address different aspects of the topic. For example, if you are reviewing literature about women and religion, key themes can include the role of women in churches and the religious attitude towards women.
• Qualitative versus quantitative research
• Empirical versus theoretical scholarship
• Divide the research by sociological, historical, or cultural sources
• Theoretical : In many humanities articles, the literature review is the foundation for the theoretical framework. You can use it to discuss various theories, models, and definitions of key concepts. You can argue for the relevance of a specific theoretical approach or combine various theorical concepts to create a framework for your research.

What are some strategies or tips I can use while writing my lit review?

Any lit review is only as good as the research it discusses; make sure your sources are well-chosen and your research is thorough. Don’t be afraid to do more research if you discover a new thread as you’re writing. More info on the research process is available in our "Conducting Research" resources .

As you’re doing your research, create an annotated bibliography ( see our page on the this type of document ). Much of the information used in an annotated bibliography can be used also in a literature review, so you’ll be not only partially drafting your lit review as you research, but also developing your sense of the larger conversation going on among scholars, professionals, and any other stakeholders in your topic.

Usually you will need to synthesize research rather than just summarizing it. This means drawing connections between sources to create a picture of the scholarly conversation on a topic over time. Many student writers struggle to synthesize because they feel they don’t have anything to add to the scholars they are citing; here are some strategies to help you:

• It often helps to remember that the point of these kinds of syntheses is to show your readers how you understand your research, to help them read the rest of your paper.
• Writing teachers often say synthesis is like hosting a dinner party: imagine all your sources are together in a room, discussing your topic. What are they saying to each other?
• Look at the in-text citations in each paragraph. Are you citing just one source for each paragraph? This usually indicates summary only. When you have multiple sources cited in a paragraph, you are more likely to be synthesizing them (not always, but often
• Read more about synthesis here.

The most interesting literature reviews are often written as arguments (again, as mentioned at the beginning of the page, this is discipline-specific and doesn’t work for all situations). Often, the literature review is where you can establish your research as filling a particular gap or as relevant in a particular way. You have some chance to do this in your introduction in an article, but the literature review section gives a more extended opportunity to establish the conversation in the way you would like your readers to see it. You can choose the intellectual lineage you would like to be part of and whose definitions matter most to your thinking (mostly humanities-specific, but this goes for sciences as well). In addressing these points, you argue for your place in the conversation, which tends to make the lit review more compelling than a simple reporting of other sources.

How do I Write a Literature Review?: #5 Writing the Review

• Step #1: Choosing a Topic
• Step #2: Finding Information
• Step #3: Evaluating Content
• Step #4: Synthesizing Content
• #5 Writing the Review
• Citing Your Sources

WRITING THE REVIEW 

You've done the research and now you're ready to put your findings down on paper. When preparing to write your review, first consider how will you organize your review.

The actual review generally has 5 components:

Abstract  -  An abstract is a summary of your literature review. It is made up of the following parts:

• A contextual sentence about your motivation behind your research topic
• Your thesis statement
• A descriptive statement about the types of literature used in the review
• Summarize your findings
• Conclusion(s) based upon your findings

Introduction :   Like a typical research paper introduction, provide the reader with a quick idea of the topic of the literature review:

• Define or identify the general topic, issue, or area of concern. This provides the reader with context for reviewing the literature.
• Identify related trends in what has already been published about the topic; or conflicts in theory, methodology, evidence, and conclusions; or gaps in research and scholarship; or a single problem or new perspective of immediate interest.
• Establish your reason (point of view) for reviewing the literature; explain the criteria to be used in analyzing and comparing literature and the organization of the review (sequence); and, when necessary, state why certain literature is or is not included (scope)  - 

Body :  The body of a literature review contains your discussion of sources and can be organized in 3 ways-

• Chronological -  by publication or by trend
• Thematic -  organized around a topic or issue, rather than the progression of time
• Methodical -  the focusing factor usually does not have to do with the content of the material. Instead, it focuses on the "methods" of the literature's researcher or writer that you are reviewing

You may also want to include a section on "questions for further research" and discuss what questions the review has sparked about the topic/field or offer suggestions for future studies/examinations that build on your current findings.

Conclusion :  In the conclusion, you should:

Conclude your paper by providing your reader with some perspective on the relationship between your literature review's specific topic and how it's related to it's parent discipline, scientific endeavor, or profession.

Bibliography :   Since a literature review is composed of pieces of research, it is very important that your correctly cite the literature you are reviewing, both in the reviews body as well as in a bibliography/works cited. To learn more about different citation styles, visit the " Citing Your Sources " tab.

• Writing a Literature Review: Wesleyan University
• Literature Review: Edith Cowan University
• << Previous: Step #4: Synthesizing Content
• Next: Citing Your Sources >>
• Last Updated: Aug 22, 2023 1:35 PM
• URL: https://libguides.eastern.edu/literature_reviews

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How To Write A Literature Review - A Complete Guide

Table of Contents

A literature review is much more than just another section in your research paper. It forms the very foundation of your research. It is a formal piece of writing where you analyze the existing theoretical framework, principles, and assumptions and use that as a base to shape your approach to the research question.

Curating and drafting a solid literature review section not only lends more credibility to your research paper but also makes your research tighter and better focused. But, writing literature reviews is a difficult task. It requires extensive reading, plus you have to consider market trends and technological and political changes, which tend to change in the blink of an eye.

Now streamline your literature review process with the help of SciSpace Copilot. With this AI research assistant, you can efficiently synthesize and analyze a vast amount of information, identify key themes and trends, and uncover gaps in the existing research. Get real-time explanations, summaries, and answers to your questions for the paper you're reviewing, making navigating and understanding the complex literature landscape easier.

In this comprehensive guide, we will explore everything from the definition of a literature review, its appropriate length, various types of literature reviews, and how to write one.

What is a literature review?

A literature review is a collation of survey, research, critical evaluation, and assessment of the existing literature in a preferred domain.

Eminent researcher and academic Arlene Fink, in her book Conducting Research Literature Reviews , defines it as the following:

“A literature review surveys books, scholarly articles, and any other sources relevant to a particular issue, area of research, or theory, and by so doing, provides a description, summary, and critical evaluation of these works in relation to the research problem being investigated.

Literature reviews are designed to provide an overview of sources you have explored while researching a particular topic, and to demonstrate to your readers how your research fits within a larger field of study.”

Simply put, a literature review can be defined as a critical discussion of relevant pre-existing research around your research question and carving out a definitive place for your study in the existing body of knowledge. Literature reviews can be presented in multiple ways: a section of an article, the whole research paper itself, or a chapter of your thesis.

A literature review does function as a summary of sources, but it also allows you to analyze further, interpret, and examine the stated theories, methods, viewpoints, and, of course, the gaps in the existing content.

As an author, you can discuss and interpret the research question and its various aspects and debate your adopted methods to support the claim.

What is the purpose of a literature review?

A literature review is meant to help your readers understand the relevance of your research question and where it fits within the existing body of knowledge. As a researcher, you should use it to set the context, build your argument, and establish the need for your study.

What is the importance of a literature review?

The literature review is a critical part of research papers because it helps you:

• Gain an in-depth understanding of your research question and the surrounding area
• Convey that you have a thorough understanding of your research area and are up-to-date with the latest changes and advancements
• Establish how your research is connected or builds on the existing body of knowledge and how it could contribute to further research
• Elaborate on the validity and suitability of your theoretical framework and research methodology
• Identify and highlight gaps and shortcomings in the existing body of knowledge and how things need to change
• Convey to readers how your study is different or how it contributes to the research area

How long should a literature review be?

Ideally, the literature review should take up 15%-40% of the total length of your manuscript. So, if you have a 10,000-word research paper, the minimum word count could be 1500.

Your literature review format depends heavily on the kind of manuscript you are writing — an entire chapter in case of doctoral theses, a part of the introductory section in a research article, to a full-fledged review article that examines the previously published research on a topic.

Another determining factor is the type of research you are doing. The literature review section tends to be longer for secondary research projects than primary research projects.

What are the different types of literature reviews?

All literature reviews are not the same. There are a variety of possible approaches that you can take. It all depends on the type of research you are pursuing.

Here are the different types of literature reviews:

Argumentative review

It is called an argumentative review when you carefully present literature that only supports or counters a specific argument or premise to establish a viewpoint.

Integrative review

It is a type of literature review focused on building a comprehensive understanding of a topic by combining available theoretical frameworks and empirical evidence.

Methodological review

This approach delves into the ''how'' and the ''what" of the research question —  you cannot look at the outcome in isolation; you should also review the methodology used.

Systematic review

This form consists of an overview of existing evidence pertinent to a clearly formulated research question, which uses pre-specified and standardized methods to identify and critically appraise relevant research and collect, report, and analyze data from the studies included in the review.

Meta-analysis review

Meta-analysis uses statistical methods to summarize the results of independent studies. By combining information from all relevant studies, meta-analysis can provide more precise estimates of the effects than those derived from the individual studies included within a review.

Historical review

Historical literature reviews focus on examining research throughout a period, often starting with the first time an issue, concept, theory, or phenomenon emerged in the literature, then tracing its evolution within the scholarship of a discipline. The purpose is to place research in a historical context to show familiarity with state-of-the-art developments and identify future research's likely directions.

Theoretical Review

This form aims to examine the corpus of theory accumulated regarding an issue, concept, theory, and phenomenon. The theoretical literature review helps to establish what theories exist, the relationships between them, the degree the existing approaches have been investigated, and to develop new hypotheses to be tested.

Scoping Review

The Scoping Review is often used at the beginning of an article, dissertation, or research proposal. It is conducted before the research to highlight gaps in the existing body of knowledge and explains why the project should be greenlit.

State-of-the-Art Review

The State-of-the-Art review is conducted periodically, focusing on the most recent research. It describes what is currently known, understood, or agreed upon regarding the research topic and highlights where there are still disagreements.

Can you use the first person in a literature review?

When writing literature reviews, you should avoid the usage of first-person pronouns. It means that instead of "I argue that" or "we argue that," the appropriate expression would be "this research paper argues that."

Do you need an abstract for a literature review?

Ideally, yes. It is always good to have a condensed summary that is self-contained and independent of the rest of your review. As for how to draft one, you can follow the same fundamental idea when preparing an abstract for a literature review. It should also include:

• The research topic and your motivation behind selecting it
• A one-sentence thesis statement
• An explanation of the kinds of literature featured in the review
• Summary of what you've learned
• Conclusions you drew from the literature you reviewed
• Potential implications and future scope for research

Here's an example of the abstract of a literature review

Is a literature review written in the past tense?

Yes, the literature review should ideally be written in the past tense. You should not use the present or future tense when writing one. The exceptions are when you have statements describing events that happened earlier than the literature you are reviewing or events that are currently occurring; then, you can use the past perfect or present perfect tenses.

How many sources for a literature review?

There are multiple approaches to deciding how many sources to include in a literature review section. The first approach would be to look level you are at as a researcher. For instance, a doctoral thesis might need 60+ sources. In contrast, you might only need to refer to 5-15 sources at the undergraduate level.

The second approach is based on the kind of literature review you are doing — whether it is merely a chapter of your paper or if it is a self-contained paper in itself. When it is just a chapter, sources should equal the total number of pages in your article's body. In the second scenario, you need at least three times as many sources as there are pages in your work.

Quick tips on how to write a literature review

To know how to write a literature review, you must clearly understand its impact and role in establishing your work as substantive research material.

You need to follow the below-mentioned steps, to write a literature review:

• Outline the purpose behind the literature review
• Search relevant literature
• Examine and assess the relevant resources
• Discover connections by drawing deep insights from the resources
• Structure planning to write a good literature review

1. Outline and identify the purpose of  a literature review

As a first step on how to write a literature review, you must know what the research question or topic is and what shape you want your literature review to take. Ensure you understand the research topic inside out, or else seek clarifications. You must be able to the answer below questions before you start:

• How many sources do I need to include?
• What kind of sources should I analyze?
• How much should I critically evaluate each source?
• Should I summarize, synthesize or offer a critique of the sources?
• Do I need to include any background information or definitions?

Additionally, you should know that the narrower your research topic is, the swifter it will be for you to restrict the number of sources to be analyzed.

2. Search relevant literature

Dig deeper into search engines to discover what has already been published around your chosen topic. Make sure you thoroughly go through appropriate reference sources like books, reports, journal articles, government docs, and web-based resources.

You must prepare a list of keywords and their different variations. You can start your search from any library’s catalog, provided you are an active member of that institution. The exact keywords can be extended to widen your research over other databases and academic search engines like:

• Google Scholar
• Microsoft Academic
• Science.gov

Besides, it is not advisable to go through every resource word by word. Alternatively, what you can do is you can start by reading the abstract and then decide whether that source is relevant to your research or not.

Additionally, you must spend surplus time assessing the quality and relevance of resources. It would help if you tried preparing a list of citations to ensure that there lies no repetition of authors, publications, or articles in the literature review.

3. Examine and assess the sources

It is nearly impossible for you to go through every detail in the research article. So rather than trying to fetch every detail, you have to analyze and decide which research sources resemble closest and appear relevant to your chosen domain.

While analyzing the sources, you should look to find out answers to questions like:

• What question or problem has the author been describing and debating?
• What is the definition of critical aspects?
• How well the theories, approach, and methodology have been explained?
• Whether the research theory used some conventional or new innovative approach?
• How relevant are the key findings of the work?
• In what ways does it relate to other sources on the same topic?
• What challenges does this research paper pose to the existing theory
• What are the possible contributions or benefits it adds to the subject domain?

Be always mindful that you refer only to credible and authentic resources. It would be best if you always take references from different publications to validate your theory.

Always keep track of important information or data you can present in your literature review right from the beginning. It will help steer your path from any threats of plagiarism and also make it easier to curate an annotated bibliography or reference section.

4. Discover connections

At this stage, you must start deciding on the argument and structure of your literature review. To accomplish this, you must discover and identify the relations and connections between various resources while drafting your abstract.

A few aspects that you should be aware of while writing a literature review include:

• Rise to prominence: Theories and methods that have gained reputation and supporters over time.
• Constant scrutiny: Concepts or theories that repeatedly went under examination.
• Contradictions and conflicts: Theories, both the supporting and the contradictory ones, for the research topic.
• Knowledge gaps: What exactly does it fail to address, and how to bridge them with further research?
• Influential resources: Significant research projects available that have been upheld as milestones or perhaps, something that can modify the current trends

Once you join the dots between various past research works, it will be easier for you to draw a conclusion and identify your contribution to the existing knowledge base.

5. Structure planning to write a good literature review

There exist different ways towards planning and executing the structure of a literature review. The format of a literature review varies and depends upon the length of the research.

Like any other research paper, the literature review format must contain three sections: introduction, body, and conclusion. The goals and objectives of the research question determine what goes inside these three sections.

Nevertheless, a good literature review can be structured according to the chronological, thematic, methodological, or theoretical framework approach.

Literature review samples

1. Standalone

2. As a section of a research paper

How SciSpace Discover makes literature review a breeze?

SciSpace Discover is a one-stop solution to do an effective literature search and get barrier-free access to scientific knowledge. It is an excellent repository where you can find millions of only peer-reviewed articles and full-text PDF files. Here’s more on how you can use it:

Find the right information

Find what you want quickly and easily with comprehensive search filters that let you narrow down papers according to PDF availability, year of publishing, document type, and affiliated institution. Moreover, you can sort the results based on the publishing date, citation count, and relevance.

Assess credibility of papers quickly

When doing the literature review, it is critical to establish the quality of your sources. They form the foundation of your research. SciSpace Discover helps you assess the quality of a source by providing an overview of its references, citations, and performance metrics.

Get the complete picture in no time

SciSpace Discover’s personalized suggestion engine helps you stay on course and get the complete picture of the topic from one place. Every time you visit an article page, it provides you links to related papers. Besides that, it helps you understand what’s trending, who are the top authors, and who are the leading publishers on a topic.

Make referring sources super easy

To ensure you don't lose track of your sources, you must start noting down your references when doing the literature review. SciSpace Discover makes this step effortless. Click the 'cite' button on an article page, and you will receive preloaded citation text in multiple styles — all you've to do is copy-paste it into your manuscript.

Final tips on how to write a literature review

A massive chunk of time and effort is required to write a good literature review. But, if you go about it systematically, you'll be able to save a ton of time and build a solid foundation for your research.

We hope this guide has helped you answer several key questions you have about writing literature reviews.

Would you like to explore SciSpace Discover and kick off your literature search right away? You can get started here .

Frequently Asked Questions (FAQs)

1. how to start a literature review.

• What questions do you want to answer?

• What sources do you need to answer these questions?

• What information do these sources contain?

• How can you use this information to answer your questions?

2. What to include in a literature review?

• A brief background of the problem or issue

• What has previously been done to address the problem or issue

• A description of what you will do in your project

• How this study will contribute to research on the subject

3. Why literature review is important?

The literature review is an important part of any research project because it allows the writer to look at previous studies on a topic and determine existing gaps in the literature, as well as what has already been done. It will also help them to choose the most appropriate method for their own study.

4. How to cite a literature review in APA format?

To cite a literature review in APA style, you need to provide the author's name, the title of the article, and the year of publication. For example: Patel, A. B., & Stokes, G. S. (2012). The relationship between personality and intelligence: A meta-analysis of longitudinal research. Personality and Individual Differences, 53(1), 16-21

5. What are the components of a literature review?

• A brief introduction to the topic, including its background and context. The introduction should also include a rationale for why the study is being conducted and what it will accomplish.

• A description of the methodologies used in the study. This can include information about data collection methods, sample size, and statistical analyses.

• A presentation of the findings in an organized format that helps readers follow along with the author's conclusions.

6. What are common errors in writing literature review?

• Not spending enough time to critically evaluate the relevance of resources, observations and conclusions.

• Totally relying on secondary data while ignoring primary data.

• Letting your personal bias seep into your interpretation of existing literature.

• No detailed explanation of the procedure to discover and identify an appropriate literature review.

7. What are the 5 C's of writing literature review?

• Cite - the sources you utilized and referenced in your research.

• Compare - existing arguments, hypotheses, methodologies, and conclusions found in the knowledge base.

• Contrast - the arguments, topics, methodologies, approaches, and disputes that may be found in the literature.

• Critique - the literature and describe the ideas and opinions you find more convincing and why.

• Connect - the various studies you reviewed in your research.

8. How many sources should a literature review have?

When it is just a chapter, sources should equal the total number of pages in your article's body. if it is a self-contained paper in itself, you need at least three times as many sources as there are pages in your work.

9. Can literature review have diagrams?

• To represent an abstract idea or concept

• To explain the steps of a process or procedure

• To help readers understand the relationships between different concepts

10. How old should sources be in a literature review?

Sources for a literature review should be as current as possible or not older than ten years. The only exception to this rule is if you are reviewing a historical topic and need to use older sources.

11. What are the types of literature review?

• Argumentative review

• Integrative review

• Methodological review

• Systematic review

• Meta-analysis review

• Historical review

• Theoretical review

• Scoping review

• State-of-the-Art review

12. Is a literature review mandatory?

Yes. Literature review is a mandatory part of any research project. It is a critical step in the process that allows you to establish the scope of your research, and provide a background for the rest of your work.

But before you go,

• Six Online Tools for Easy Literature Review
• Evaluating literature review: systematic vs. scoping reviews
• Systematic Approaches to a Successful Literature Review
• Writing Integrative Literature Reviews: Guidelines and Examples

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7 Writing a Literature Review

Hundreds of original investigation research articles on health science topics are published each year. It is becoming harder and harder to keep on top of all new findings in a topic area and – more importantly – to work out how they all fit together to determine our current understanding of a topic. This is where literature reviews come in.

In this chapter, we explain what a literature review is and outline the stages involved in writing one. We also provide practical tips on how to communicate the results of a review of current literature on a topic in the format of a literature review.

7.1 What is a literature review?

Literature reviews provide a synthesis and evaluation  of the existing literature on a particular topic with the aim of gaining a new, deeper understanding of the topic.

Published literature reviews are typically written by scientists who are experts in that particular area of science. Usually, they will be widely published as authors of their own original work, making them highly qualified to author a literature review.

However, literature reviews are still subject to peer review before being published. Literature reviews provide an important bridge between the expert scientific community and many other communities, such as science journalists, teachers, and medical and allied health professionals. When the most up-to-date knowledge reaches such audiences, it is more likely that this information will find its way to the general public. When this happens, – the ultimate good of science can be realised.

A literature review is structured differently from an original research article. It is developed based on themes, rather than stages of the scientific method.

In the article Ten simple rules for writing a literature review , Marco Pautasso explains the importance of literature reviews:

Literature reviews are in great demand in most scientific fields. Their need stems from the ever-increasing output of scientific publications. For example, compared to 1991, in 2008 three, eight, and forty times more papers were indexed in Web of Science on malaria, obesity, and biodiversity, respectively. Given such mountains of papers, scientists cannot be expected to examine in detail every single new paper relevant to their interests. Thus, it is both advantageous and necessary to rely on regular summaries of the recent literature. Although recognition for scientists mainly comes from primary research, timely literature reviews can lead to new synthetic insights and are often widely read. For such summaries to be useful, however, they need to be compiled in a professional way (Pautasso, 2013, para. 1).

An example of a literature review is shown in Figure 7.1.

Video 7.1: What is a literature review? [2 mins, 11 secs]

Watch this video created by Steely Library at Northern Kentucky Library called ‘ What is a literature review? Note: Closed captions are available by clicking on the CC button below.

Examples of published literature reviews

• Strength training alone, exercise therapy alone, and exercise therapy with passive manual mobilisation each reduce pain and disability in people with knee osteoarthritis: a systematic review
• Traveler’s diarrhea: a clinical review
• Cultural concepts of distress and psychiatric disorders: literature review and research recommendations for global mental health epidemiology

7.2 Steps of writing a literature review

Writing a literature review is a very challenging task. Figure 7.2 summarises the steps of writing a literature review. Depending on why you are writing your literature review, you may be given a topic area, or may choose a topic that particularly interests you or is related to a research project that you wish to undertake.

Chapter 6 provides instructions on finding scientific literature that would form the basis for your literature review.

Once you have your topic and have accessed the literature, the next stages (analysis, synthesis and evaluation) are challenging. Next, we look at these important cognitive skills student scientists will need to develop and employ to successfully write a literature review, and provide some guidance for navigating these stages.

Analysis, synthesis and evaluation

Analysis, synthesis and evaluation are three essential skills required by scientists  and you will need to develop these skills if you are to write a good literature review ( Figure 7.3 ). These important cognitive skills are discussed in more detail in Chapter 9.

The first step in writing a literature review is to analyse the original investigation research papers that you have gathered related to your topic.

Analysis requires examining the papers methodically and in detail, so you can understand and interpret aspects of the study described in each research article.

An analysis grid is a simple tool you can use to help with the careful examination and breakdown of each paper. This tool will allow you to create a concise summary of each research paper; see Table 7.1 for an example of  an analysis grid. When filling in the grid, the aim is to draw out key aspects of each research paper. Use a different row for each paper, and a different column for each aspect of the paper ( Tables 7.2 and 7.3 show how completed analysis grid may look).

Before completing your own grid, look at these examples and note the types of information that have been included, as well as the level of detail. Completing an analysis grid with a sufficient level of detail will help you to complete the synthesis and evaluation stages effectively. This grid will allow you to more easily observe similarities and differences across the findings of the research papers and to identify possible explanations (e.g., differences in methodologies employed) for observed differences between the findings of different research papers.

Table 7.1: Example of an analysis grid

Table 7.3: Sample filled-in analysis grid for research article by Ping and colleagues

Source: Ping, WC, Keong, CC & Bandyopadhyay, A 2010, ‘Effects of acute supplementation of caffeine on cardiorespiratory responses during endurance running in a hot and humid climate’, Indian Journal of Medical Research, vol. 132, pp. 36–41. Used under a CC-BY-NC-SA licence.

Step two of writing a literature review is synthesis.

Synthesis describes combining separate components or elements to form a connected whole.

You will use the results of your analysis to find themes to build your literature review around. Each of the themes identified will become a subheading within the body of your literature review.

A good place to start when identifying themes is with the dependent variables (results/findings) that were investigated in the research studies.

Because all of the research articles you are incorporating into your literature review are related to your topic, it is likely that they have similar study designs and have measured similar dependent variables. Review the ‘Results’ column of your analysis grid. You may like to collate the common themes in a synthesis grid (see, for example Table 7.4 ).

Step three of writing a literature review is evaluation, which can only be done after carefully analysing your research papers and synthesising the common themes (findings).

During the evaluation stage, you are making judgements on the themes presented in the research articles that you have read. This includes providing physiological explanations for the findings. It may be useful to refer to the discussion section of published original investigation research papers, or another literature review, where the authors may mention tested or hypothetical physiological mechanisms that may explain their findings.

When the findings of the investigations related to a particular theme are inconsistent (e.g., one study shows that caffeine effects performance and another study shows that caffeine had no effect on performance) you should attempt to provide explanations of why the results differ, including physiological explanations. A good place to start is by comparing the methodologies to determine if there are any differences that may explain the differences in the findings (see the ‘Experimental design’ column of your analysis grid). An example of evaluation is shown in the examples that follow in this section, under ‘Running performance’ and ‘RPE ratings’.

When the findings of the papers related to a particular theme are consistent (e.g., caffeine had no effect on oxygen uptake in both studies) an evaluation should include an explanation of why the results are similar. Once again, include physiological explanations. It is still a good idea to compare methodologies as a background to the evaluation. An example of evaluation is shown in the following under ‘Oxygen consumption’.

7.3 Writing your literature review

Once you have completed the analysis, and synthesis grids and written your evaluation of the research papers , you can combine synthesis and evaluation information to create a paragraph for a literature review ( Figure 7.4 ).

The following paragraphs are an example of combining the outcome of the synthesis and evaluation stages to produce a paragraph for a literature review.

Note that this is an example using only two papers – most literature reviews would be presenting information on many more papers than this ( (e.g., 106 papers in the review article by Bain and colleagues discussed later in this chapter). However, the same principle applies regardless of the number of papers reviewed.

The next part of this chapter looks at the each section of a literature review and explains how to write them by referring to a review article that was published in Frontiers in Physiology and shown in Figure 7.1. Each section from the published article is annotated to highlight important features of the format of the review article, and identifies the synthesis and evaluation information.

In the examination of each review article section we will point out examples of how the authors have presented certain information and where they display application of important cognitive processes; we will use the colour code shown below:

This should be one paragraph that accurately reflects the contents of the review article.

Introduction

The introduction should establish the context and importance of the review

Body of literature review

The reference section provides a list of the references that you cited in the body of your review article. The format will depend on the journal of publication as each journal has their own specific referencing format.

It is important to accurately cite references in research papers to acknowledge your sources and ensure credit is appropriately given to authors of work you have referred to. An accurate and comprehensive reference list also shows your readers that you are well-read in your topic area and are aware of the key papers that provide the context to your research.

It is important to keep track of your resources and to reference them consistently in the format required by the publication in which your work will appear. Most scientists will use reference management software to store details of all of the journal articles (and other sources) they use while writing their review article. This software also automates the process of adding in-text references and creating a reference list. In the review article by Bain et al. (2014) used as an example in this chapter, the reference list contains 106 items, so you can imagine how much help referencing software would be. Chapter 5 shows you how to use EndNote, one example of reference management software.

Click the drop down below to review the terms learned from this chapter.

Copyright note:

• The quotation from Pautasso, M 2013, ‘Ten simple rules for writing a literature review’, PLoS Computational Biology is use under a CC-BY licence. 
• Content from the annotated article and tables are based on Schubert, MM, Astorino, TA & Azevedo, JJL 2013, ‘The effects of caffeinated ‘energy shots’ on time trial performance’, Nutrients, vol. 5, no. 6, pp. 2062–2075 (used under a CC-BY 3.0 licence ) and P ing, WC, Keong , CC & Bandyopadhyay, A 2010, ‘Effects of acute supplementation of caffeine on cardiorespiratory responses during endurance running in a hot and humid climate’, Indian Journal of Medical Research, vol. 132, pp. 36–41 (used under a CC-BY-NC-SA 4.0 licence ). 

Bain, A.R., Morrison, S.A., & Ainslie, P.N. (2014). Cerebral oxygenation and hyperthermia. Frontiers in Physiology, 5 , 92.

Pautasso, M. (2013). Ten simple rules for writing a literature review. PLoS Computational Biology, 9 (7), e1003149.

How To Do Science Copyright © 2022 by University of Southern Queensland is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License , except where otherwise noted.

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Writing an Abstract for Your Research Paper

Definition and Purpose of Abstracts

An abstract is a short summary of your (published or unpublished) research paper, usually about a paragraph (c. 6-7 sentences, 150-250 words) long. A well-written abstract serves multiple purposes:

• an abstract lets readers get the gist or essence of your paper or article quickly, in order to decide whether to read the full paper;
• an abstract prepares readers to follow the detailed information, analyses, and arguments in your full paper;
• and, later, an abstract helps readers remember key points from your paper.

It’s also worth remembering that search engines and bibliographic databases use abstracts, as well as the title, to identify key terms for indexing your published paper. So what you include in your abstract and in your title are crucial for helping other researchers find your paper or article.

If you are writing an abstract for a course paper, your professor may give you specific guidelines for what to include and how to organize your abstract. Similarly, academic journals often have specific requirements for abstracts. So in addition to following the advice on this page, you should be sure to look for and follow any guidelines from the course or journal you’re writing for.

The Contents of an Abstract

Abstracts contain most of the following kinds of information in brief form. The body of your paper will, of course, develop and explain these ideas much more fully. As you will see in the samples below, the proportion of your abstract that you devote to each kind of information—and the sequence of that information—will vary, depending on the nature and genre of the paper that you are summarizing in your abstract. And in some cases, some of this information is implied, rather than stated explicitly. The Publication Manual of the American Psychological Association , which is widely used in the social sciences, gives specific guidelines for what to include in the abstract for different kinds of papers—for empirical studies, literature reviews or meta-analyses, theoretical papers, methodological papers, and case studies.

Here are the typical kinds of information found in most abstracts:

• the context or background information for your research; the general topic under study; the specific topic of your research
• the central questions or statement of the problem your research addresses
• what’s already known about this question, what previous research has done or shown
• the main reason(s) , the exigency, the rationale , the goals for your research—Why is it important to address these questions? Are you, for example, examining a new topic? Why is that topic worth examining? Are you filling a gap in previous research? Applying new methods to take a fresh look at existing ideas or data? Resolving a dispute within the literature in your field? . . .
• your research and/or analytical methods
• your main findings , results , or arguments
• the significance or implications of your findings or arguments.

Your abstract should be intelligible on its own, without a reader’s having to read your entire paper. And in an abstract, you usually do not cite references—most of your abstract will describe what you have studied in your research and what you have found and what you argue in your paper. In the body of your paper, you will cite the specific literature that informs your research.

When to Write Your Abstract

Although you might be tempted to write your abstract first because it will appear as the very first part of your paper, it’s a good idea to wait to write your abstract until after you’ve drafted your full paper, so that you know what you’re summarizing.

What follows are some sample abstracts in published papers or articles, all written by faculty at UW-Madison who come from a variety of disciplines. We have annotated these samples to help you see the work that these authors are doing within their abstracts.

Choosing Verb Tenses within Your Abstract

The social science sample (Sample 1) below uses the present tense to describe general facts and interpretations that have been and are currently true, including the prevailing explanation for the social phenomenon under study. That abstract also uses the present tense to describe the methods, the findings, the arguments, and the implications of the findings from their new research study. The authors use the past tense to describe previous research.

The humanities sample (Sample 2) below uses the past tense to describe completed events in the past (the texts created in the pulp fiction industry in the 1970s and 80s) and uses the present tense to describe what is happening in those texts, to explain the significance or meaning of those texts, and to describe the arguments presented in the article.

The science samples (Samples 3 and 4) below use the past tense to describe what previous research studies have done and the research the authors have conducted, the methods they have followed, and what they have found. In their rationale or justification for their research (what remains to be done), they use the present tense. They also use the present tense to introduce their study (in Sample 3, “Here we report . . .”) and to explain the significance of their study (In Sample 3, This reprogramming . . . “provides a scalable cell source for. . .”).

Sample Abstract 1

From the social sciences.

Reporting new findings about the reasons for increasing economic homogamy among spouses

Gonalons-Pons, Pilar, and Christine R. Schwartz. “Trends in Economic Homogamy: Changes in Assortative Mating or the Division of Labor in Marriage?” Demography , vol. 54, no. 3, 2017, pp. 985-1005.

Sample Abstract 2

From the humanities.

Analyzing underground pulp fiction publications in Tanzania, this article makes an argument about the cultural significance of those publications

Emily Callaci. “Street Textuality: Socialism, Masculinity, and Urban Belonging in Tanzania’s Pulp Fiction Publishing Industry, 1975-1985.” Comparative Studies in Society and History , vol. 59, no. 1, 2017, pp. 183-210.

Sample Abstract/Summary 3

From the sciences.

Reporting a new method for reprogramming adult mouse fibroblasts into induced cardiac progenitor cells

Lalit, Pratik A., Max R. Salick, Daryl O. Nelson, Jayne M. Squirrell, Christina M. Shafer, Neel G. Patel, Imaan Saeed, Eric G. Schmuck, Yogananda S. Markandeya, Rachel Wong, Martin R. Lea, Kevin W. Eliceiri, Timothy A. Hacker, Wendy C. Crone, Michael Kyba, Daniel J. Garry, Ron Stewart, James A. Thomson, Karen M. Downs, Gary E. Lyons, and Timothy J. Kamp. “Lineage Reprogramming of Fibroblasts into Proliferative Induced Cardiac Progenitor Cells by Defined Factors.” Cell Stem Cell , vol. 18, 2016, pp. 354-367.

Sample Abstract 4, a Structured Abstract

Reporting results about the effectiveness of antibiotic therapy in managing acute bacterial sinusitis, from a rigorously controlled study

Note: This journal requires authors to organize their abstract into four specific sections, with strict word limits. Because the headings for this structured abstract are self-explanatory, we have chosen not to add annotations to this sample abstract.

Wald, Ellen R., David Nash, and Jens Eickhoff. “Effectiveness of Amoxicillin/Clavulanate Potassium in the Treatment of Acute Bacterial Sinusitis in Children.” Pediatrics , vol. 124, no. 1, 2009, pp. 9-15.

“OBJECTIVE: The role of antibiotic therapy in managing acute bacterial sinusitis (ABS) in children is controversial. The purpose of this study was to determine the effectiveness of high-dose amoxicillin/potassium clavulanate in the treatment of children diagnosed with ABS.

METHODS : This was a randomized, double-blind, placebo-controlled study. Children 1 to 10 years of age with a clinical presentation compatible with ABS were eligible for participation. Patients were stratified according to age (<6 or ≥6 years) and clinical severity and randomly assigned to receive either amoxicillin (90 mg/kg) with potassium clavulanate (6.4 mg/kg) or placebo. A symptom survey was performed on days 0, 1, 2, 3, 5, 7, 10, 20, and 30. Patients were examined on day 14. Children’s conditions were rated as cured, improved, or failed according to scoring rules.

RESULTS: Two thousand one hundred thirty-five children with respiratory complaints were screened for enrollment; 139 (6.5%) had ABS. Fifty-eight patients were enrolled, and 56 were randomly assigned. The mean age was 6630 months. Fifty (89%) patients presented with persistent symptoms, and 6 (11%) presented with nonpersistent symptoms. In 24 (43%) children, the illness was classified as mild, whereas in the remaining 32 (57%) children it was severe. Of the 28 children who received the antibiotic, 14 (50%) were cured, 4 (14%) were improved, 4(14%) experienced treatment failure, and 6 (21%) withdrew. Of the 28children who received placebo, 4 (14%) were cured, 5 (18%) improved, and 19 (68%) experienced treatment failure. Children receiving the antibiotic were more likely to be cured (50% vs 14%) and less likely to have treatment failure (14% vs 68%) than children receiving the placebo.

CONCLUSIONS : ABS is a common complication of viral upper respiratory infections. Amoxicillin/potassium clavulanate results in significantly more cures and fewer failures than placebo, according to parental report of time to resolution.” (9)

Some Excellent Advice about Writing Abstracts for Basic Science Research Papers, by Professor Adriano Aguzzi from the Institute of Neuropathology at the University of Zurich:

Academic and Professional Writing

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• Get more help with your essay
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Proposals and Dissertations

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Quoting and Paraphrasing

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Creating Poster Presentations

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Reading for a Review

Critical Reviews

Writing a Review of Literature

Scientific Reports

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11.8  Writing an abstract

All full reviews must include an abstract of not more than 400 words. The abstract should be kept as brief as possible without sacrificing important content. Abstracts to Cochrane reviews are published in MEDLINE and the Science Citation Index, and are made freely available on the internet. It is therefore important that they can be read as stand-alone documents.

The abstract should summarize the key methods, results and conclusions of the review and should not contain any information that is not in the review. Links to other parts of the review (such as references, studies, tables and figures) may not be included in the abstract. A hypothetical example of an abstract is included in Box 11.8.a .

Abstracts should be targeted primarily at healthcare decision makers (clinicians, informed consumers and policy makers) rather than just to researchers. Terminology should be reasonably comprehensible to a general rather than a specialist healthcare audience. Abbreviations should be avoided, except where they are widely understood (for example, HIV). Where essential, other abbreviations should be spelt out (with the abbreviations in brackets) on first use. Names of drugs and interventions that can be understood internationally should be used wherever possible. Trade names should not be used.

The content under each heading in the abstract should be as follows:

Background: This should be one or two sentences to explain the context or elaborate on the purpose and rationale of the review. If this version of the review is an update of an earlier one, it is helpful to include a sentence such as “This is an update of a Cochrane review first published in YEAR, and previously updated in YEAR”.

Objectives:  This should be a precise statement of the primary objective of the review, ideally in a single sentence, matching the Objectives in the main text of the review. Where possible the style should be of the form “To assess the effects of   [intervention or comparison] for [health problem] for/in [types of people, disease or problem and setting if specified]”.

Search methods: This should list the sources and the dates of the last search, for each source, using the active form ‘We searched….’ or, if there is only one author, the passive form can be used, for example, ‘Database X, Y, Z were searched’. Search terms should not be listed here. If the CRG’s Specialized Register was used, this should be listed first in the form ‘Cochrane X Group Specialized Register’. The order for listing other databases should be the Cochrane Central Register of Controlled Trials, MEDLINE, EMBASE, other databases. The date range of the search for each database should be given. For the Cochrane Central Register of Controlled Trials this should be in the form ‘Cochrane Central Register of Controlled Trials ( The Cochrane Library 2007, Issue 1)’. For most other databases, such as MEDLINE, it should be in the form ‘MEDLINE (January 1966 to December 2006)’. Searching of bibliographies for relevant citations can be covered in a generic phrase ‘reference lists of articles’. If there were any constraints based on language or publication status, these should be listed. If individuals or organizations were contacted to locate studies this should be noted and it is preferable to use ‘We contacted pharmaceutical companies’ rather than a listing of all the pharmaceutical companies contacted. If journals were specifically handsearched for the review, this should be noted but handsearching to help build the Specialized Register of the CRG should not be listed.

Selection criteria: These should be given as ‘ [type of study] of [type of intervention or comparison] in [disease, problem or type of people]‘ . Outcomes should only be listed here if the review was restricted to specific outcomes.

Data collection and analysis: This should be restricted to how data were extracted and assessed, and not include details of what data were extracted. This section should cover whether data extraction and assessments of risk of bias were done by more than one person. If the authors contacted investigators to obtain missing information, this should be noted here. What steps, if any, were taken to identify adverse effects should be noted.

Main results: This section should begin with the total number of studies and participants included in the review, and brief details pertinent to the interpretation of the results (for example, the risk of bias in the studies overall or a comment on the comparability of the studies, if appropriate). It should address the primary objective and be restricted to the main qualitative and quantitative results (generally including not more than six key results). The outcomes included should be selected on the basis of which are most likely to help someone making a decision about whether or not to use a particular intervention. Adverse effects should be included if these are covered in the review. If necessary, the number of studies and participants contributing to the separate outcomes should be noted, along with concerns over quality of evidence specific to these outcomes. The results should be expressed narratively as well as quantitatively if the numerical results are not clear or intuitive (such as those from a standardized mean differences analysis). The summary statistics in the abstract should be the same as those selected as the defaults for the review, and should be presented in a standard way, such as ‘odds ratio 2.31 (95% confidence interval 1.13 to 3.45)’. Ideally, risks of events (percentage) or averages (for continuous data) should be reported for both comparison groups. If overall results are not calculated in the review, a qualitative assessment or a description of the range and pattern of the results can be given. However, ‘vote counts’ in which the numbers of ‘positive’ and ‘negative’ studies are reported should be avoided.

Authors’ conclusions: The primary purpose of the review should be to present information, rather than to offer advice or recommendations. The Authors’ conclusions should be succinct and drawn directly from the findings of the review so that they directly and obviously reflect the main results. Assumptions should generally not be made about practice circumstances, values, preferences, tradeoffs; and the giving of advice or recommendations should generally be avoided. Any important limitations of data and analyses should be noted. Important conclusions about the implications for research should be included if these are not obvious.

What this handout is about

This handout provides definitions and examples of the two main types of abstracts: descriptive and informative. It also provides guidelines for constructing an abstract and general tips for you to keep in mind when drafting. Finally, it includes a few examples of abstracts broken down into their component parts.

What is an abstract?

An abstract is a self-contained, short, and powerful statement that describes a larger work. Components vary according to discipline. An abstract of a social science or scientific work may contain the scope, purpose, results, and contents of the work. An abstract of a humanities work may contain the thesis, background, and conclusion of the larger work. An abstract is not a review, nor does it evaluate the work being abstracted. While it contains key words found in the larger work, the abstract is an original document rather than an excerpted passage.

Why write an abstract?

You may write an abstract for various reasons. The two most important are selection and indexing. Abstracts allow readers who may be interested in a longer work to quickly decide whether it is worth their time to read it. Also, many online databases use abstracts to index larger works. Therefore, abstracts should contain keywords and phrases that allow for easy searching.

Say you are beginning a research project on how Brazilian newspapers helped Brazil’s ultra-liberal president Luiz Ignácio da Silva wrest power from the traditional, conservative power base. A good first place to start your research is to search Dissertation Abstracts International for all dissertations that deal with the interaction between newspapers and politics. “Newspapers and politics” returned 569 hits. A more selective search of “newspapers and Brazil” returned 22 hits. That is still a fair number of dissertations. Titles can sometimes help winnow the field, but many titles are not very descriptive. For example, one dissertation is titled “Rhetoric and Riot in Rio de Janeiro.” It is unclear from the title what this dissertation has to do with newspapers in Brazil. One option would be to download or order the entire dissertation on the chance that it might speak specifically to the topic. A better option is to read the abstract. In this case, the abstract reveals the main focus of the dissertation:

This dissertation examines the role of newspaper editors in the political turmoil and strife that characterized late First Empire Rio de Janeiro (1827-1831). Newspaper editors and their journals helped change the political culture of late First Empire Rio de Janeiro by involving the people in the discussion of state. This change in political culture is apparent in Emperor Pedro I’s gradual loss of control over the mechanisms of power. As the newspapers became more numerous and powerful, the Emperor lost his legitimacy in the eyes of the people. To explore the role of the newspapers in the political events of the late First Empire, this dissertation analyzes all available newspapers published in Rio de Janeiro from 1827 to 1831. Newspapers and their editors were leading forces in the effort to remove power from the hands of the ruling elite and place it under the control of the people. In the process, newspapers helped change how politics operated in the constitutional monarchy of Brazil.

From this abstract you now know that although the dissertation has nothing to do with modern Brazilian politics, it does cover the role of newspapers in changing traditional mechanisms of power. After reading the abstract, you can make an informed judgment about whether the dissertation would be worthwhile to read.

Besides selection, the other main purpose of the abstract is for indexing. Most article databases in the online catalog of the library enable you to search abstracts. This allows for quick retrieval by users and limits the extraneous items recalled by a “full-text” search. However, for an abstract to be useful in an online retrieval system, it must incorporate the key terms that a potential researcher would use to search. For example, if you search Dissertation Abstracts International using the keywords “France” “revolution” and “politics,” the search engine would search through all the abstracts in the database that included those three words. Without an abstract, the search engine would be forced to search titles, which, as we have seen, may not be fruitful, or else search the full text. It’s likely that a lot more than 60 dissertations have been written with those three words somewhere in the body of the entire work. By incorporating keywords into the abstract, the author emphasizes the central topics of the work and gives prospective readers enough information to make an informed judgment about the applicability of the work.

When do people write abstracts?

• when submitting articles to journals, especially online journals
• when applying for research grants
• when writing a book proposal
• when completing the Ph.D. dissertation or M.A. thesis
• when writing a proposal for a conference paper
• when writing a proposal for a book chapter

Most often, the author of the entire work (or prospective work) writes the abstract. However, there are professional abstracting services that hire writers to draft abstracts of other people’s work. In a work with multiple authors, the first author usually writes the abstract. Undergraduates are sometimes asked to draft abstracts of books/articles for classmates who have not read the larger work.

Types of abstracts

There are two types of abstracts: descriptive and informative. They have different aims, so as a consequence they have different components and styles. There is also a third type called critical, but it is rarely used. If you want to find out more about writing a critique or a review of a work, see the UNC Writing Center handout on writing a literature review . If you are unsure which type of abstract you should write, ask your instructor (if the abstract is for a class) or read other abstracts in your field or in the journal where you are submitting your article.

Descriptive abstracts

A descriptive abstract indicates the type of information found in the work. It makes no judgments about the work, nor does it provide results or conclusions of the research. It does incorporate key words found in the text and may include the purpose, methods, and scope of the research. Essentially, the descriptive abstract describes the work being abstracted. Some people consider it an outline of the work, rather than a summary. Descriptive abstracts are usually very short—100 words or less.

Informative abstracts

The majority of abstracts are informative. While they still do not critique or evaluate a work, they do more than describe it. A good informative abstract acts as a surrogate for the work itself. That is, the writer presents and explains all the main arguments and the important results and evidence in the complete article/paper/book. An informative abstract includes the information that can be found in a descriptive abstract (purpose, methods, scope) but also includes the results and conclusions of the research and the recommendations of the author. The length varies according to discipline, but an informative abstract is rarely more than 10% of the length of the entire work. In the case of a longer work, it may be much less.

Here are examples of a descriptive and an informative abstract of this handout on abstracts . Descriptive abstract:

The two most common abstract types—descriptive and informative—are described and examples of each are provided.

Informative abstract:

Abstracts present the essential elements of a longer work in a short and powerful statement. The purpose of an abstract is to provide prospective readers the opportunity to judge the relevance of the longer work to their projects. Abstracts also include the key terms found in the longer work and the purpose and methods of the research. Authors abstract various longer works, including book proposals, dissertations, and online journal articles. There are two main types of abstracts: descriptive and informative. A descriptive abstract briefly describes the longer work, while an informative abstract presents all the main arguments and important results. This handout provides examples of various types of abstracts and instructions on how to construct one.

Which type should I use?

Your best bet in this case is to ask your instructor or refer to the instructions provided by the publisher. You can also make a guess based on the length allowed; i.e., 100-120 words = descriptive; 250+ words = informative.

How do I write an abstract?

The format of your abstract will depend on the work being abstracted. An abstract of a scientific research paper will contain elements not found in an abstract of a literature article, and vice versa. However, all abstracts share several mandatory components, and there are also some optional parts that you can decide to include or not. When preparing to draft your abstract, keep the following key process elements in mind:

• Reason for writing: What is the importance of the research? Why would a reader be interested in the larger work?
• Problem: What problem does this work attempt to solve? What is the scope of the project? What is the main argument/thesis/claim?
• Methodology: An abstract of a scientific work may include specific models or approaches used in the larger study. Other abstracts may describe the types of evidence used in the research.
• Results: Again, an abstract of a scientific work may include specific data that indicates the results of the project. Other abstracts may discuss the findings in a more general way.
• Implications: What changes should be implemented as a result of the findings of the work? How does this work add to the body of knowledge on the topic?

(This list of elements is adapted with permission from Philip Koopman, “How to Write an Abstract.” )

All abstracts include:

• A full citation of the source, preceding the abstract.
• The most important information first.
• The same type and style of language found in the original, including technical language.
• Key words and phrases that quickly identify the content and focus of the work.
• Clear, concise, and powerful language.

Abstracts may include:

• The thesis of the work, usually in the first sentence.
• Background information that places the work in the larger body of literature.
• The same chronological structure as the original work.

How not to write an abstract:

• Do not refer extensively to other works.
• Do not add information not contained in the original work.
• Do not define terms.

If you are abstracting your own writing

When abstracting your own work, it may be difficult to condense a piece of writing that you have agonized over for weeks (or months, or even years) into a 250-word statement. There are some tricks that you could use to make it easier, however.

Reverse outlining:

This technique is commonly used when you are having trouble organizing your own writing. The process involves writing down the main idea of each paragraph on a separate piece of paper– see our short video . For the purposes of writing an abstract, try grouping the main ideas of each section of the paper into a single sentence. Practice grouping ideas using webbing or color coding .

For a scientific paper, you may have sections titled Purpose, Methods, Results, and Discussion. Each one of these sections will be longer than one paragraph, but each is grouped around a central idea. Use reverse outlining to discover the central idea in each section and then distill these ideas into one statement.

Cut and paste:

To create a first draft of an abstract of your own work, you can read through the entire paper and cut and paste sentences that capture key passages. This technique is useful for social science research with findings that cannot be encapsulated by neat numbers or concrete results. A well-written humanities draft will have a clear and direct thesis statement and informative topic sentences for paragraphs or sections. Isolate these sentences in a separate document and work on revising them into a unified paragraph.

If you are abstracting someone else’s writing

When abstracting something you have not written, you cannot summarize key ideas just by cutting and pasting. Instead, you must determine what a prospective reader would want to know about the work. There are a few techniques that will help you in this process:

Identify key terms:

Search through the entire document for key terms that identify the purpose, scope, and methods of the work. Pay close attention to the Introduction (or Purpose) and the Conclusion (or Discussion). These sections should contain all the main ideas and key terms in the paper. When writing the abstract, be sure to incorporate the key terms.

Highlight key phrases and sentences:

Instead of cutting and pasting the actual words, try highlighting sentences or phrases that appear to be central to the work. Then, in a separate document, rewrite the sentences and phrases in your own words.

Don’t look back:

After reading the entire work, put it aside and write a paragraph about the work without referring to it. In the first draft, you may not remember all the key terms or the results, but you will remember what the main point of the work was. Remember not to include any information you did not get from the work being abstracted.

Revise, revise, revise

No matter what type of abstract you are writing, or whether you are abstracting your own work or someone else’s, the most important step in writing an abstract is to revise early and often. When revising, delete all extraneous words and incorporate meaningful and powerful words. The idea is to be as clear and complete as possible in the shortest possible amount of space. The Word Count feature of Microsoft Word can help you keep track of how long your abstract is and help you hit your target length.

Example 1: Humanities abstract

Kenneth Tait Andrews, “‘Freedom is a constant struggle’: The dynamics and consequences of the Mississippi Civil Rights Movement, 1960-1984” Ph.D. State University of New York at Stony Brook, 1997 DAI-A 59/02, p. 620, Aug 1998

This dissertation examines the impacts of social movements through a multi-layered study of the Mississippi Civil Rights Movement from its peak in the early 1960s through the early 1980s. By examining this historically important case, I clarify the process by which movements transform social structures and the constraints movements face when they try to do so. The time period studied includes the expansion of voting rights and gains in black political power, the desegregation of public schools and the emergence of white-flight academies, and the rise and fall of federal anti-poverty programs. I use two major research strategies: (1) a quantitative analysis of county-level data and (2) three case studies. Data have been collected from archives, interviews, newspapers, and published reports. This dissertation challenges the argument that movements are inconsequential. Some view federal agencies, courts, political parties, or economic elites as the agents driving institutional change, but typically these groups acted in response to the leverage brought to bear by the civil rights movement. The Mississippi movement attempted to forge independent structures for sustaining challenges to local inequities and injustices. By propelling change in an array of local institutions, movement infrastructures had an enduring legacy in Mississippi.

Now let’s break down this abstract into its component parts to see how the author has distilled his entire dissertation into a ~200 word abstract.

What the dissertation does This dissertation examines the impacts of social movements through a multi-layered study of the Mississippi Civil Rights Movement from its peak in the early 1960s through the early 1980s. By examining this historically important case, I clarify the process by which movements transform social structures and the constraints movements face when they try to do so.

How the dissertation does it The time period studied in this dissertation includes the expansion of voting rights and gains in black political power, the desegregation of public schools and the emergence of white-flight academies, and the rise and fall of federal anti-poverty programs. I use two major research strategies: (1) a quantitative analysis of county-level data and (2) three case studies.

What materials are used Data have been collected from archives, interviews, newspapers, and published reports.

Conclusion This dissertation challenges the argument that movements are inconsequential. Some view federal agencies, courts, political parties, or economic elites as the agents driving institutional change, but typically these groups acted in response to movement demands and the leverage brought to bear by the civil rights movement. The Mississippi movement attempted to forge independent structures for sustaining challenges to local inequities and injustices. By propelling change in an array of local institutions, movement infrastructures had an enduring legacy in Mississippi.

Keywords social movements Civil Rights Movement Mississippi voting rights desegregation

Example 2: Science Abstract

Luis Lehner, “Gravitational radiation from black hole spacetimes” Ph.D. University of Pittsburgh, 1998 DAI-B 59/06, p. 2797, Dec 1998

The problem of detecting gravitational radiation is receiving considerable attention with the construction of new detectors in the United States, Europe, and Japan. The theoretical modeling of the wave forms that would be produced in particular systems will expedite the search for and analysis of detected signals. The characteristic formulation of GR is implemented to obtain an algorithm capable of evolving black holes in 3D asymptotically flat spacetimes. Using compactification techniques, future null infinity is included in the evolved region, which enables the unambiguous calculation of the radiation produced by some compact source. A module to calculate the waveforms is constructed and included in the evolution algorithm. This code is shown to be second-order convergent and to handle highly non-linear spacetimes. In particular, we have shown that the code can handle spacetimes whose radiation is equivalent to a galaxy converting its whole mass into gravitational radiation in one second. We further use the characteristic formulation to treat the region close to the singularity in black hole spacetimes. The code carefully excises a region surrounding the singularity and accurately evolves generic black hole spacetimes with apparently unlimited stability.

This science abstract covers much of the same ground as the humanities one, but it asks slightly different questions.

Why do this study The problem of detecting gravitational radiation is receiving considerable attention with the construction of new detectors in the United States, Europe, and Japan. The theoretical modeling of the wave forms that would be produced in particular systems will expedite the search and analysis of the detected signals.

What the study does The characteristic formulation of GR is implemented to obtain an algorithm capable of evolving black holes in 3D asymptotically flat spacetimes. Using compactification techniques, future null infinity is included in the evolved region, which enables the unambiguous calculation of the radiation produced by some compact source. A module to calculate the waveforms is constructed and included in the evolution algorithm.

Results This code is shown to be second-order convergent and to handle highly non-linear spacetimes. In particular, we have shown that the code can handle spacetimes whose radiation is equivalent to a galaxy converting its whole mass into gravitational radiation in one second. We further use the characteristic formulation to treat the region close to the singularity in black hole spacetimes. The code carefully excises a region surrounding the singularity and accurately evolves generic black hole spacetimes with apparently unlimited stability.

Keywords gravitational radiation (GR) spacetimes black holes

Works consulted

We consulted these works while writing this handout. This is not a comprehensive list of resources on the handout’s topic, and we encourage you to do your own research to find additional publications. Please do not use this list as a model for the format of your own reference list, as it may not match the citation style you are using. For guidance on formatting citations, please see the UNC Libraries citation tutorial . We revise these tips periodically and welcome feedback.

Belcher, Wendy Laura. 2009. Writing Your Journal Article in Twelve Weeks: A Guide to Academic Publishing Success. Thousand Oaks, CA: Sage Press.

Koopman, Philip. 1997. “How to Write an Abstract.” Carnegie Mellon University. October 1997. http://users.ece.cmu.edu/~koopman/essays/abstract.html .

Lancaster, F.W. 2003. Indexing And Abstracting in Theory and Practice , 3rd ed. London: Facet Publishing.

You may reproduce it for non-commercial use if you use the entire handout and attribute the source: The Writing Center, University of North Carolina at Chapel Hill

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Q: How can I write a conference abstract based on a literature review paper?

I'm working on a literature review paper (narrative type), and I would like to participate in a conference (oral presentation) with a literature review. I have to write an abstract about it, and I wonder if it is common to write conference abstracts about reviews. If yes, do you have any tips?

Asked by ABDELJALIL CHOUGRADI on 21 Oct, 2018

It is unusual to present literature reviews in a conference. Conferences are aimed at presenting and discussing the latest and the most happening or hot topics in a particular subject area. Narrative reviews are best published in a journal. I am not sure if the conference you are planning to attend even accepts an abstract related to a narrative review; please confirm this with them. What  I am also not sure of is what type of conference you are attending and the subject area that it covers, but the audience in a conference is perhaps not the correct target for a narrative/literature review since they would be more interested in knowing what is happening at the forefront of the research activities in a given field. 

In any case, the abstract for a narrative/literature review for a journal article should start with two lines of background information on the topic being discussed in the review. This should be followed by one sentence of the aim of the review. Then, in the next 2-3 sentences, you should describe the methods that you have used – you need to specify which databases you have searched, how many articles you have reviewed, the time-frame of the articles. You should next state the main observations from the review that you have performed in 2-3 sentences. As concluding remarks – in 1-2 sentences, you should state what is the inference and what is your opinion about the findings from the literature review. You can make some general recommendations and should close the abstract by stating the larger implications of the findings.

Related reading:

• How to network at a conference
• 9 Tips for presenting at an academic conference

Answered by Editage Insights on 26 Oct, 2018

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How to Write an Abstract | Steps & Examples

Published on 1 March 2019 by Shona McCombes . Revised on 10 October 2022 by Eoghan Ryan.

An abstract is a short summary of a longer work (such as a dissertation or research paper ). The abstract concisely reports the aims and outcomes of your research, so that readers know exactly what your paper is about.

Although the structure may vary slightly depending on your discipline, your abstract should describe the purpose of your work, the methods you’ve used, and the conclusions you’ve drawn.

One common way to structure your abstract is to use the IMRaD structure. This stands for:

• Introduction

Abstracts are usually around 100–300 words, but there’s often a strict word limit, so make sure to check the relevant requirements.

In a dissertation or thesis , include the abstract on a separate page, after the title page and acknowledgements but before the table of contents .

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Table of contents

Abstract example, when to write an abstract, step 1: introduction, step 2: methods, step 3: results, step 4: discussion, tips for writing an abstract, frequently asked questions about abstracts.

Hover over the different parts of the abstract to see how it is constructed.

This paper examines the role of silent movies as a mode of shared experience in the UK during the early twentieth century. At this time, high immigration rates resulted in a significant percentage of non-English-speaking citizens. These immigrants faced numerous economic and social obstacles, including exclusion from public entertainment and modes of discourse (newspapers, theater, radio).

Incorporating evidence from reviews, personal correspondence, and diaries, this study demonstrates that silent films were an affordable and inclusive source of entertainment. It argues for the accessible economic and representational nature of early cinema. These concerns are particularly evident in the low price of admission and in the democratic nature of the actors’ exaggerated gestures, which allowed the plots and action to be easily grasped by a diverse audience despite language barriers.

Keywords: silent movies, immigration, public discourse, entertainment, early cinema, language barriers.

Prevent plagiarism, run a free check.

You will almost always have to include an abstract when:

• Completing a thesis or dissertation
• Submitting a research paper to an academic journal
• Writing a book proposal
• Applying for research grants

It’s easiest to write your abstract last, because it’s a summary of the work you’ve already done. Your abstract should:

• Be a self-contained text, not an excerpt from your paper
• Be fully understandable on its own
• Reflect the structure of your larger work

Start by clearly defining the purpose of your research. What practical or theoretical problem does the research respond to, or what research question did you aim to answer?

You can include some brief context on the social or academic relevance of your topic, but don’t go into detailed background information. If your abstract uses specialised terms that would be unfamiliar to the average academic reader or that have various different meanings, give a concise definition.

After identifying the problem, state the objective of your research. Use verbs like “investigate,” “test,” “analyse,” or “evaluate” to describe exactly what you set out to do.

This part of the abstract can be written in the present or past simple tense  but should never refer to the future, as the research is already complete.

• This study will investigate the relationship between coffee consumption and productivity.
• This study investigates the relationship between coffee consumption and productivity.

Next, indicate the research methods that you used to answer your question. This part should be a straightforward description of what you did in one or two sentences. It is usually written in the past simple tense, as it refers to completed actions.

• Structured interviews will be conducted with 25 participants.
• Structured interviews were conducted with 25 participants.

Don’t evaluate validity or obstacles here — the goal is not to give an account of the methodology’s strengths and weaknesses, but to give the reader a quick insight into the overall approach and procedures you used.

Next, summarise the main research results . This part of the abstract can be in the present or past simple tense.

• Our analysis has shown a strong correlation between coffee consumption and productivity.
• Our analysis shows a strong correlation between coffee consumption and productivity.
• Our analysis showed a strong correlation between coffee consumption and productivity.

Depending on how long and complex your research is, you may not be able to include all results here. Try to highlight only the most important findings that will allow the reader to understand your conclusions.

Finally, you should discuss the main conclusions of your research : what is your answer to the problem or question? The reader should finish with a clear understanding of the central point that your research has proved or argued. Conclusions are usually written in the present simple tense.

• We concluded that coffee consumption increases productivity.
• We conclude that coffee consumption increases productivity.

If there are important limitations to your research (for example, related to your sample size or methods), you should mention them briefly in the abstract. This allows the reader to accurately assess the credibility and generalisability of your research.

If your aim was to solve a practical problem, your discussion might include recommendations for implementation. If relevant, you can briefly make suggestions for further research.

If your paper will be published, you might have to add a list of keywords at the end of the abstract. These keywords should reference the most important elements of the research to help potential readers find your paper during their own literature searches.

Be aware that some publication manuals, such as APA Style , have specific formatting requirements for these keywords.

It can be a real challenge to condense your whole work into just a couple of hundred words, but the abstract will be the first (and sometimes only) part that people read, so it’s important to get it right. These strategies can help you get started.

Read other abstracts

The best way to learn the conventions of writing an abstract in your discipline is to read other people’s. You probably already read lots of journal article abstracts while conducting your literature review —try using them as a framework for structure and style.

You can also find lots of dissertation abstract examples in thesis and dissertation databases .

Reverse outline

Not all abstracts will contain precisely the same elements. For longer works, you can write your abstract through a process of reverse outlining.

For each chapter or section, list keywords and draft one to two sentences that summarise the central point or argument. This will give you a framework of your abstract’s structure. Next, revise the sentences to make connections and show how the argument develops.

Write clearly and concisely

A good abstract is short but impactful, so make sure every word counts. Each sentence should clearly communicate one main point.

To keep your abstract or summary short and clear:

• Avoid passive sentences: Passive constructions are often unnecessarily long. You can easily make them shorter and clearer by using the active voice.
• Avoid long sentences: Substitute longer expressions for concise expressions or single words (e.g., “In order to” for “To”).
• Avoid obscure jargon: The abstract should be understandable to readers who are not familiar with your topic.
• Avoid repetition and filler words: Replace nouns with pronouns when possible and eliminate unnecessary words.
• Avoid detailed descriptions: An abstract is not expected to provide detailed definitions, background information, or discussions of other scholars’ work. Instead, include this information in the body of your thesis or paper.

If you’re struggling to edit down to the required length, you can get help from expert editors with Scribbr’s professional proofreading services .

Check your formatting

If you are writing a thesis or dissertation or submitting to a journal, there are often specific formatting requirements for the abstract—make sure to check the guidelines and format your work correctly. For APA research papers you can follow the APA abstract format .

Checklist: Abstract

The word count is within the required length, or a maximum of one page.

The abstract appears after the title page and acknowledgements and before the table of contents .

I have clearly stated my research problem and objectives.

I have briefly described my methodology .

I have summarized the most important results .

I have stated my main conclusions .

I have mentioned any important limitations and recommendations.

The abstract can be understood by someone without prior knowledge of the topic.

You've written a great abstract! Use the other checklists to continue improving your thesis or dissertation.

An abstract is a concise summary of an academic text (such as a journal article or dissertation ). It serves two main purposes:

• To help potential readers determine the relevance of your paper for their own research.
• To communicate your key findings to those who don’t have time to read the whole paper.

Abstracts are often indexed along with keywords on academic databases, so they make your work more easily findable. Since the abstract is the first thing any reader sees, it’s important that it clearly and accurately summarises the contents of your paper.

An abstract for a thesis or dissertation is usually around 150–300 words. There’s often a strict word limit, so make sure to check your university’s requirements.

The abstract is the very last thing you write. You should only write it after your research is complete, so that you can accurately summarize the entirety of your thesis or paper.

Avoid citing sources in your abstract . There are two reasons for this:

• The abstract should focus on your original research, not on the work of others.
• The abstract should be self-contained and fully understandable without reference to other sources.

There are some circumstances where you might need to mention other sources in an abstract: for example, if your research responds directly to another study or focuses on the work of a single theorist. In general, though, don’t include citations unless absolutely necessary.

The abstract appears on its own page, after the title page and acknowledgements but before the table of contents .

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What is a Literature Review?

According to the Writing Center at University of North Carolina at Chapel Hill , "A literature review discusses published information in a particular subject area, and sometimes information in a particular subject area within a certain time period."

Although a literature review may summarize research on a given topic, it generally synthesizes and summarizes a subject. The purpose of a literature review therefore is to present summaries and analysis of current research not contribute new ideas on the topic (making it different from a research paper).

Search for Literature Reviews

How to Write a Literature Review

• Learn How to Write a Review of Literature (The University of Wisconsin)
• The Literature Review: A Few Tips On Conducting It (University of Totonto)
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• Teaching the Literature Review Details strategies on how to teach students about literature reviews and how to create their own reviews.

Dos and Don'ts of a Literature Review

Make a clear statement of the research problem. Keep it in discussion style. Give a critical assessment of your chosen literature topic, try to state the weaknesses and gaps in previous studies, try to raise questions and give suggestions for improvement.

List your ideas or theories in an unrepeated and sensible sequence. Write a complete bibliography that provides the resources from where you had collected the data in this literature review.

Use unfamiliar technical terms or too many abbreviations. Use passive voice in your text. Repeat same ideas in your text. Include any ideas that you read in the article without citing them (author's name, publication date) as a reference source. Include punctuation and grammatical errors.

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What is a Literature Review? How to Write It (with Examples)

A literature review is a critical analysis and synthesis of existing research on a particular topic. It provides an overview of the current state of knowledge, identifies gaps, and highlights key findings in the literature. 1 The purpose of a literature review is to situate your own research within the context of existing scholarship, demonstrating your understanding of the topic and showing how your work contributes to the ongoing conversation in the field. Learning how to write a literature review is a critical tool for successful research. Your ability to summarize and synthesize prior research pertaining to a certain topic demonstrates your grasp on the topic of study, and assists in the learning process. 

Table of Contents

• What is the purpose of literature review? 
• a. Habitat Loss and Species Extinction: 
• b. Range Shifts and Phenological Changes: 
• c. Ocean Acidification and Coral Reefs: 
• d. Adaptive Strategies and Conservation Efforts: 
• How to write a good literature review 
• Choose a Topic and Define the Research Question: 
• Decide on the Scope of Your Review: 
• Select Databases for Searches: 
• Conduct Searches and Keep Track: 
• Review the Literature: 
• Organize and Write Your Literature Review: 
• Frequently asked questions 

What is a literature review?

A well-conducted literature review demonstrates the researcher’s familiarity with the existing literature, establishes the context for their own research, and contributes to scholarly conversations on the topic. One of the purposes of a literature review is also to help researchers avoid duplicating previous work and ensure that their research is informed by and builds upon the existing body of knowledge.

What is the purpose of literature review?

A literature review serves several important purposes within academic and research contexts. Here are some key objectives and functions of a literature review: 2  

• Contextualizing the Research Problem: The literature review provides a background and context for the research problem under investigation. It helps to situate the study within the existing body of knowledge. 
• Identifying Gaps in Knowledge: By identifying gaps, contradictions, or areas requiring further research, the researcher can shape the research question and justify the significance of the study. This is crucial for ensuring that the new research contributes something novel to the field. 
• Understanding Theoretical and Conceptual Frameworks: Literature reviews help researchers gain an understanding of the theoretical and conceptual frameworks used in previous studies. This aids in the development of a theoretical framework for the current research. 
• Providing Methodological Insights: Another purpose of literature reviews is that it allows researchers to learn about the methodologies employed in previous studies. This can help in choosing appropriate research methods for the current study and avoiding pitfalls that others may have encountered. 
• Establishing Credibility: A well-conducted literature review demonstrates the researcher’s familiarity with existing scholarship, establishing their credibility and expertise in the field. It also helps in building a solid foundation for the new research. 
• Informing Hypotheses or Research Questions: The literature review guides the formulation of hypotheses or research questions by highlighting relevant findings and areas of uncertainty in existing literature. 

Literature review example

Let’s delve deeper with a literature review example: Let’s say your literature review is about the impact of climate change on biodiversity. You might format your literature review into sections such as the effects of climate change on habitat loss and species extinction, phenological changes, and marine biodiversity. Each section would then summarize and analyze relevant studies in those areas, highlighting key findings and identifying gaps in the research. The review would conclude by emphasizing the need for further research on specific aspects of the relationship between climate change and biodiversity. The following literature review template provides a glimpse into the recommended literature review structure and content, demonstrating how research findings are organized around specific themes within a broader topic. 

Literature Review on Climate Change Impacts on Biodiversity:

Climate change is a global phenomenon with far-reaching consequences, including significant impacts on biodiversity. This literature review synthesizes key findings from various studies: 

a. Habitat Loss and Species Extinction:

Climate change-induced alterations in temperature and precipitation patterns contribute to habitat loss, affecting numerous species (Thomas et al., 2004). The review discusses how these changes increase the risk of extinction, particularly for species with specific habitat requirements. 

b. Range Shifts and Phenological Changes:

Observations of range shifts and changes in the timing of biological events (phenology) are documented in response to changing climatic conditions (Parmesan & Yohe, 2003). These shifts affect ecosystems and may lead to mismatches between species and their resources. 

c. Ocean Acidification and Coral Reefs:

The review explores the impact of climate change on marine biodiversity, emphasizing ocean acidification’s threat to coral reefs (Hoegh-Guldberg et al., 2007). Changes in pH levels negatively affect coral calcification, disrupting the delicate balance of marine ecosystems. 

d. Adaptive Strategies and Conservation Efforts:

Recognizing the urgency of the situation, the literature review discusses various adaptive strategies adopted by species and conservation efforts aimed at mitigating the impacts of climate change on biodiversity (Hannah et al., 2007). It emphasizes the importance of interdisciplinary approaches for effective conservation planning. 

How to write a good literature review

Writing a literature review involves summarizing and synthesizing existing research on a particular topic. A good literature review format should include the following elements. 

Introduction: The introduction sets the stage for your literature review, providing context and introducing the main focus of your review. 

• Opening Statement: Begin with a general statement about the broader topic and its significance in the field. 
• Scope and Purpose: Clearly define the scope of your literature review. Explain the specific research question or objective you aim to address. 
• Organizational Framework: Briefly outline the structure of your literature review, indicating how you will categorize and discuss the existing research. 
• Significance of the Study: Highlight why your literature review is important and how it contributes to the understanding of the chosen topic. 
• Thesis Statement: Conclude the introduction with a concise thesis statement that outlines the main argument or perspective you will develop in the body of the literature review. 

Body: The body of the literature review is where you provide a comprehensive analysis of existing literature, grouping studies based on themes, methodologies, or other relevant criteria. 

• Organize by Theme or Concept: Group studies that share common themes, concepts, or methodologies. Discuss each theme or concept in detail, summarizing key findings and identifying gaps or areas of disagreement. 
• Critical Analysis: Evaluate the strengths and weaknesses of each study. Discuss the methodologies used, the quality of evidence, and the overall contribution of each work to the understanding of the topic. 
• Synthesis of Findings: Synthesize the information from different studies to highlight trends, patterns, or areas of consensus in the literature. 
• Identification of Gaps: Discuss any gaps or limitations in the existing research and explain how your review contributes to filling these gaps. 
• Transition between Sections: Provide smooth transitions between different themes or concepts to maintain the flow of your literature review. 

Conclusion: The conclusion of your literature review should summarize the main findings, highlight the contributions of the review, and suggest avenues for future research. 

• Summary of Key Findings: Recap the main findings from the literature and restate how they contribute to your research question or objective. 
• Contributions to the Field: Discuss the overall contribution of your literature review to the existing knowledge in the field. 
• Implications and Applications: Explore the practical implications of the findings and suggest how they might impact future research or practice. 
• Recommendations for Future Research: Identify areas that require further investigation and propose potential directions for future research in the field. 
• Final Thoughts: Conclude with a final reflection on the importance of your literature review and its relevance to the broader academic community. 

Conducting a literature review

Conducting a literature review is an essential step in research that involves reviewing and analyzing existing literature on a specific topic. It’s important to know how to do a literature review effectively, so here are the steps to follow: 1  

Choose a Topic and Define the Research Question:

• Select a topic that is relevant to your field of study. 
• Clearly define your research question or objective. Determine what specific aspect of the topic do you want to explore? 

Decide on the Scope of Your Review:

• Determine the timeframe for your literature review. Are you focusing on recent developments, or do you want a historical overview? 
• Consider the geographical scope. Is your review global, or are you focusing on a specific region? 
• Define the inclusion and exclusion criteria. What types of sources will you include? Are there specific types of studies or publications you will exclude? 

Select Databases for Searches:

• Identify relevant databases for your field. Examples include PubMed, IEEE Xplore, Scopus, Web of Science, and Google Scholar. 
• Consider searching in library catalogs, institutional repositories, and specialized databases related to your topic. 

Conduct Searches and Keep Track:

• Develop a systematic search strategy using keywords, Boolean operators (AND, OR, NOT), and other search techniques. 
• Record and document your search strategy for transparency and replicability. 
• Keep track of the articles, including publication details, abstracts, and links. Use citation management tools like EndNote, Zotero, or Mendeley to organize your references. 

Review the Literature:

• Evaluate the relevance and quality of each source. Consider the methodology, sample size, and results of studies. 
• Organize the literature by themes or key concepts. Identify patterns, trends, and gaps in the existing research. 
• Summarize key findings and arguments from each source. Compare and contrast different perspectives. 
• Identify areas where there is a consensus in the literature and where there are conflicting opinions. 
• Provide critical analysis and synthesis of the literature. What are the strengths and weaknesses of existing research? 

Organize and Write Your Literature Review:

• Literature review outline should be based on themes, chronological order, or methodological approaches. 
• Write a clear and coherent narrative that synthesizes the information gathered. 
• Use proper citations for each source and ensure consistency in your citation style (APA, MLA, Chicago, etc.). 
• Conclude your literature review by summarizing key findings, identifying gaps, and suggesting areas for future research. 

The literature review sample and detailed advice on writing and conducting a review will help you produce a well-structured report. But remember that a literature review is an ongoing process, and it may be necessary to revisit and update it as your research progresses. 

Frequently asked questions

A literature review is a critical and comprehensive analysis of existing literature (published and unpublished works) on a specific topic or research question and provides a synthesis of the current state of knowledge in a particular field. A well-conducted literature review is crucial for researchers to build upon existing knowledge, avoid duplication of efforts, and contribute to the advancement of their field. It also helps researchers situate their work within a broader context and facilitates the development of a sound theoretical and conceptual framework for their studies.

Literature review is a crucial component of research writing, providing a solid background for a research paper’s investigation. The aim is to keep professionals up to date by providing an understanding of ongoing developments within a specific field, including research methods, and experimental techniques used in that field, and present that knowledge in the form of a written report. Also, the depth and breadth of the literature review emphasizes the credibility of the scholar in his or her field.  

Before writing a literature review, it’s essential to undertake several preparatory steps to ensure that your review is well-researched, organized, and focused. This includes choosing a topic of general interest to you and doing exploratory research on that topic, writing an annotated bibliography, and noting major points, especially those that relate to the position you have taken on the topic. 

Literature reviews and academic research papers are essential components of scholarly work but serve different purposes within the academic realm. 3 A literature review aims to provide a foundation for understanding the current state of research on a particular topic, identify gaps or controversies, and lay the groundwork for future research. Therefore, it draws heavily from existing academic sources, including books, journal articles, and other scholarly publications. In contrast, an academic research paper aims to present new knowledge, contribute to the academic discourse, and advance the understanding of a specific research question. Therefore, it involves a mix of existing literature (in the introduction and literature review sections) and original data or findings obtained through research methods. 

Literature reviews are essential components of academic and research papers, and various strategies can be employed to conduct them effectively. If you want to know how to write a literature review for a research paper, here are four common approaches that are often used by researchers.  Chronological Review: This strategy involves organizing the literature based on the chronological order of publication. It helps to trace the development of a topic over time, showing how ideas, theories, and research have evolved.  Thematic Review: Thematic reviews focus on identifying and analyzing themes or topics that cut across different studies. Instead of organizing the literature chronologically, it is grouped by key themes or concepts, allowing for a comprehensive exploration of various aspects of the topic.  Methodological Review: This strategy involves organizing the literature based on the research methods employed in different studies. It helps to highlight the strengths and weaknesses of various methodologies and allows the reader to evaluate the reliability and validity of the research findings.  Theoretical Review: A theoretical review examines the literature based on the theoretical frameworks used in different studies. This approach helps to identify the key theories that have been applied to the topic and assess their contributions to the understanding of the subject.  It’s important to note that these strategies are not mutually exclusive, and a literature review may combine elements of more than one approach. The choice of strategy depends on the research question, the nature of the literature available, and the goals of the review. Additionally, other strategies, such as integrative reviews or systematic reviews, may be employed depending on the specific requirements of the research.

The literature review format can vary depending on the specific publication guidelines. However, there are some common elements and structures that are often followed. Here is a general guideline for the format of a literature review:  Introduction:   Provide an overview of the topic.  Define the scope and purpose of the literature review.  State the research question or objective.  Body:   Organize the literature by themes, concepts, or chronology.  Critically analyze and evaluate each source.  Discuss the strengths and weaknesses of the studies.  Highlight any methodological limitations or biases.  Identify patterns, connections, or contradictions in the existing research.  Conclusion:   Summarize the key points discussed in the literature review.  Highlight the research gap.  Address the research question or objective stated in the introduction.  Highlight the contributions of the review and suggest directions for future research.

Both annotated bibliographies and literature reviews involve the examination of scholarly sources. While annotated bibliographies focus on individual sources with brief annotations, literature reviews provide a more in-depth, integrated, and comprehensive analysis of existing literature on a specific topic. The key differences are as follows: 

References 

• Denney, A. S., & Tewksbury, R. (2013). How to write a literature review.  Journal of criminal justice education ,  24 (2), 218-234. 
• Pan, M. L. (2016).  Preparing literature reviews: Qualitative and quantitative approaches . Taylor & Francis. 
• Cantero, C. (2019). How to write a literature review.  San José State University Writing Center . 

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Home Speaker Management Best Practices for Writing an Abstract and Why You Should Integrate Abstract Management Technology

Best Practices for Writing an Abstract and Why You Should Integrate Abstract Management Technology

Marilena De Niear

April 29, 2024

Simply put, abstracts are the gateway to scholarly research. Whether you’re presenting at a conference, submitting a paper to a journal, or applying for a grant, a well-crafted abstract is crucial. It serves as a concise summary of your work, providing readers with a snapshot of your study’s objectives, methods, results, and conclusions.  

In this blog post, we’ll explore the value of an abstract, the best practices to write one, and how integrating abstract management technology, specifically content management software like Attendee Interactive, can streamline the process. 

Beginning with the basics: what is an abstract?  

An abstract is a summary of a research paper, presentation, or project. It condenses the main points of the work into a concise paragraph or a few paragraphs, enabling readers to quickly grasp the essence of the study without having to read the entire document.  

Essentially, an abstract acts as a teaser, enticing readers to delve deeper into the full text if they find the topic relevant or interesting. 

Sounds easy enough, until you’re tasked with crafting one. That’s why we’re offering a quick review of the best practices that make writing your abstract easier and the final product more polished.  

Best practices for writing an abstract  

• Clarity and conciseness : Keep your abstract clear, concise, and to the point. Avoid unnecessary jargon or technical language that may confuse readers. 
• Structure : Follow a structured format, typically including sections such as background/objective, methods, results, and conclusions. This helps readers navigate through your abstract easily. 
• Accuracy : Ensure that your abstract accurately reflects the content of your study. Avoid making exaggerated claims or misrepresenting your findings. 
• Grammar and style : Pay attention to grammar, punctuation, and style. Your abstract should be well-written and free of errors. 
• Relevance : Tailor your abstract to the specific audience or context in which it will be presented. Highlight the aspects of your research that are most relevant to the target audience. 

Integrating technology: the role of content management software  

Content management software can revolutionize the abstract submission and review process by providing features like online submission portals, peer review management, and automated notifications, streamlining the entire workflow from submission to acceptance. 

By leveraging technology, authors can easily submit their abstracts online, track the status of their submissions, and receive feedback from reviewers in a timely manner.  

Conference organizers benefit from an automated abstract submission and review process , centralized data management, efficient communication with authors and reviewers, and customizable workflows tailored to their specific requirements. 

Why are abstracts important?  

With all the focus on the best practices of writing an abstract, it’s worth a reminder about why abstracts are so valuable . Abstracts play a crucial role in academia and research for several reasons: 

• Accessibility : They provide a quick overview of a study’s key findings, making research more accessible to a wider audience. 
• Decision-making : Conference organizers, journal editors, and grant review committees often rely on abstracts to make decisions about acceptance, publication, or funding. 
• Indexing and searchability : Abstracts are indexed in databases and search engines, making it easier for researchers to discover relevant literature in their field. This is a win-win for the author and researcher.  

With an appreciation for their value firmly in place, here are a few finer points about abstracts that we’re often asked about…  

How long should an abstract be?  

The length of an abstract can vary depending on the requirements of the conference or journal. However, most abstracts are typically around 150 to 250 words — in fact, a 250-word limit is common . Some journals or conferences may specify a maximum word count, so it’s essential to check and always adhere to their guidelines . 

Who is the audience for an abstract?  

The audience for an abstract can vary depending on the context. It may include researchers, academics, conference attendees, journal editors, grant review panels, or anyone interested in the topic of the research. 

Do abstracts vary across disciplines?  

Yes, abstracts can vary across different disciplines based on conventions, expectations, and the nature of the research. For example, scientific abstracts may include sections such as hypothesis, methods, results, and conclusions, while humanities abstracts may focus more on the argument or thesis of the paper. 

Should citations or references be included in an abstract?  

In general, citations or references are not included in an abstract due to space limitations. However, some journals or conferences may allow for the inclusion of a limited number of references if necessary. It’s essential to check the specific guidelines of the venue where you’re submitting your abstract. 

Should keywords be integrated into an abstract?  

Yes, integrating keywords into an abstract can improve its visibility and searchability. Keywords should accurately reflect the main topics or themes of your research, making it easier for readers to find your work through database searches or online queries. 

Fields to include in an abstract submission  

When submitting an abstract, you may be required to provide the following fields: 

• Title : The title of your research paper or presentation. 
• Authors : The names and affiliations of the authors involved in the study. 
• Keywords : Relevant keywords or phrases to help categorize and index your abstract. 
• Discipline : The field or discipline to which your research belongs. 

Types of abstracts  

Descriptive abstract : Simply describes the topic, purpose, and scope of the study without including specific results or conclusions. 

Informative abstract : Provides a summary of the key elements of the study, including objectives, methods, results, and conclusions. 

Structured abstract : Organizes information into distinct sections, such as background, methods, results, and conclusions, for clarity and ease of reading. 

Graphical abstract : Uses visual elements such as charts, graphs, or images to summarize the main findings of the study. 

FAQ: Frequently asked questions about abstracts  

In addition to the finer points about abstracts, we’ve compiled a quick reference list of the most asked questions concerning abstracts and how to write them effectively.  

Can I include unpublished data or preliminary results in my abstract?  

Yes, abstracts often include unpublished data or preliminary results, but it’s essential to clearly indicate if the findings are preliminary or subject to change.  

Do I need to follow a specific format when writing an abstract?  

Many conferences and journals provide guidelines or templates for abstract submissions. It’s crucial to follow these guidelines to ensure that your abstract meets the requirements of the venue.  

Can I submit the same abstract to multiple conferences or journals?  

It’s generally not advisable to submit the same abstract to multiple venues simultaneously. However, you may adapt your abstract for different audiences or contexts if you disclose previous presentations or submissions.  

How can I make my abstract stand out from the rest?  

Focus on presenting your research in a clear, compelling, and engaging manner. Highlight the significance of your findings and their implications for the field. Additionally, pay attention to the language, style, and formatting of your abstract to make it visually appealing and easy to read.  

Writing an effective abstract requires careful attention to detail, clarity of expression, and adherence to guidelines. By following best practices and leveraging technology, researchers can create impactful abstracts that effectively communicate the essence of their work to a diverse audience.  

Whether you’re presenting at a conference, submitting to a journal, or applying for funding, a well-crafted abstract can significantly enhance the visibility and impact of your research. 

Let attendee interactive assist with your abstract management  

Ready to elevate your event planning and abstract management experience? Remember, a well-crafted abstract is the key to unlocking an impactful presentation.  

By harnessing effective strategies, leveraging cutting-edge abstract management technology , and embracing best practices, you can create an enriching event experience that showcases groundbreaking research and fosters meaningful connections among presenters and attendees. 

At Attendee Interactive, we offer a comprehensive abstract submission management system designed to streamline your workflow. Say goodbye to manual processes and data scattered across multiple platforms. Our system centralizes all your abstract data and provides customizable options to meet your event’s unique needs.  

With Attendee Interactive, you can efficiently collect, review, and store abstracts, ensuring a seamless experience for all stakeholders. 

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• Published: 25 April 2024

Surgery is associated with better long-term outcomes than pharmacological treatment for obesity: a systematic review and meta-analysis

• Leonardo Zumerkorn Pipek 1 ,
• Walter Augusto Fabio Moraes 2 ,
• Rodrigo Massato Nobetani 2 ,
• Vitor Santos Cortez 2 ,
• Alberto Santos Condi 2 ,
• João Victor Taba 2 ,
• Rafaela Farias Vidigal Nascimento 3 ,
• Milena Oliveira Suzuki 2 ,
• Fernanda Sayuri do Nascimento 2 ,
• Vitoria Carneiro de Mattos 2 ,
• Leandro Ryuchi Iuamoto 4 ,
• Wu Tu Hsing 4 ,
• Luiz Augusto Carneiro-D’Albuquerque 5 ,
• Alberto Meyer 5 &
• Wellington Andraus 5  

Scientific Reports volume  14 , Article number:  9521 ( 2024 ) Cite this article

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• Endocrine system and metabolic diseases
• Gastrointestinal diseases

Obesity is a highly prevalent disease with numerous complications. Both intensive medical treatment with the use of pharmacological drugs and bariatric surgery are current options. The objective of this meta-analysis was to compare, in the long-term, intensive medical treatment and surgery based on twelve parameters related to weight loss, cardiovascular and endocrine changes. A review of the literature was conducted in accordance with the PRISMA guidelines (PROSPERO: CRD42021265637). The literature screening was done from inception to October 2023 through PubMed, EMBASE and Web of Science databases. We included randomized clinical trials that had separate groups for medical treatment and bariatric surgery as an intervention for obesity. The risk of bias was assessed through RoB2. A meta-analysis was performed with measures of heterogeneity and publication bias. Subgroup analysis for each surgery type was performed. Data is presented as forest-plots. Reviewers independently identified 6719 articles and 6 papers with a total 427 patients were included. All studies were randomized controlled trials, three had a follow up of 5 years and two had a follow up of 10 years. Both groups demonstrated statistical significance for most parameters studied. Surgery was superior for weight loss (− 22.05 kg [− 28.86; − 15.23), total cholesterol (− 0.88 [− 1.59; − 0.17]), triglycerides (− 0.70 [− 0.82; − 0.59]), HDL (0.12 [0.02; 0.23]), systolic pressure (− 4.49 [− 7.65; − 1.33]), diastolic pressure (− 2.28 [− 4.25; − 0.31]), Hb glycated (− 0.97 [− 1.31; − 0.62]), HOMA IR (− 2.94; [− 3.52; − 2.35]) and cardiovascular risk (− 0.08; [− 0.10; − 0.05]). Patient in the surgical treatment group had better long term outcomes when compared to the non-surgical group for most clinical parameters.

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Development and validation of a new algorithm for improved cardiovascular risk prediction

Introduction.

Obesity has been a known condition for over 2000 years 1 but that has become much more prevalent in recent decades. Despite great efforts to prevent this disease, the prevalence in adults in the United States has increased in recent decades and reached 42.4% in 2018. The GBD Obesity Study 2 Collaborators 2015 showed that this increasing trend occurred in more than 70 countries and is highly expressive in adolescents.

The classification of obesity is defined by a body mass index (BMI) greater than 30 kg/m 2 . The psychological damage that many of these patients suffer in a society governed by aesthetic standards is just one of the most visible and immediate consequences of obesity. Mortality from cardiovascular causes and its relationship with BMI has already been widely studied 3 , showing that the risk increases progressively with the increase of the index. Similarly, obesity was associated with a higher incidence of cancer 4 , respiratory 5 and metabolic 6 diseases.

In this context, the importance of effective treatment of this condition is clear, reducing mortality and improving the quality of life of these patients. While some benefits are evident with a loss of just 5% 6 of their weight, many patients require a more expressive loss to reduce the risks associated with obesity.

There are several treatments available for weight loss. Lifestyle changes, low calorie diet and increasing physical activity are the mainstay treatment for all patients 7 , 8 . Specific weight loss diets and exercise programs have also been developed for this purpose, yielding varying results. Finally, pharmacological, and surgical treatment has gained more attention in recent years for selected patients in whom other measures were insufficient.

Several studies have demonstrated the effectiveness of bariatric surgery in the short and medium term for the treatment of obesity. More recent studies have also shown that new drugs developed for weight loss may be a viable option for the treatment of this disease 8 , 9 . Comparison of these new drugs with surgical treatment is scarce in the literature and aimed only at evaluating changes related to weight loss in a short period of time.

This systematic review evaluated the hypothesis whether surgical treatment is superior than non-surgical treatment for patients with obesity. We evaluated the long-term effect of these treatments on anthropometric measures (weight, waist circumference, BMI) and on obesity related pathologies (triglycerides, LDL, HDL, total cholesterol, cardiovascular risk, systolic and diastolic blood pressure, HOMA and glycated hemoglobin).

Materials and methods

This systematic review was carried out in accordance with the items of Preferred Reports for Systematic Reviews and Protocol Meta-Analysis (PRISMA-P) 10 and assessing the methodological quality of systematic reviews (AMSTAR-2) guidelines 11 . This study was registered by the Prospective Register of Systematic Reviews (PROSPERO, 258667) before the research was carried out.

Drafting of the research question was based on the PICO strategy 12 , considering: P (Patients with obesity with indication for bariatric surgery based on BMI); I (Bariatric Surgery); C (Pharmacological treatment); O (Long term morbidity/mortality—at least 5 years of follow up).

Eligibility criteria

Inclusion criteria.

Types of studies: Randomized clinical trials.

Types of participants: Patients eligible for bariatric surgery, according to the American Society for Metabolic and Bariatric Surgery (ASMBS).

Types of intervention: Bariatric surgery or medical treatment.

Exclusion criteria

Studies were excluded if they: (1) did not have one group for each type of intervention (surgery or pharmacologic treatment); (2) had a heterogeneous population; (3) did not use a standard assessment method for the entire duration of the study, or did not have pre-assessment; (4) were not related to the question in the review; (5) were in a language other than English, Portuguese or Spanish; (6) were incomplete, unpublished or inaccessible to the authors.

Types of variables/parameters analyzed

Data was collected and arranged in tables, including the authors name, date and country of publication, number of participants included in the final analysis, sex, age, and body mass index.

Literature revision

The survey was from inception to October 10, 2023, without language restrictions, in the Medline database (via PubMed), EMBASE and Web of Science.

Using the search tool, we selected MeSH terms from the most relevant publications to conduct a new search to obtain articles that could be included in this systematic review. In addition, a manual search of theses, meetings, references, study records and contact with experts in the field was carried out.

Search strategy

The same keywords were used in all databases, according to each database input format.

The search strategy was:

(Bariatric Surgery) AND ((nonsurgical) OR (Orlistat) OR (phentermine) OR (topiramate) OR (lorcaserin) OR (naltrexone) OR (bupropion) OR (liraglutide) OR (conservative) OR (conventional) OR (Anti-Obesity Agents) OR (Intensive medical)) AND (obesity) → 3024.

(Bariatric Surgery) AND ((nonsurgical) OR (conservative) OR (Anti-Obesity Agents) OR (Intensive medical)) AND (obesity) → 4732.

Web of Science:

(Bariatric Surgery) AND ((nonsurgical) OR (conservative) OR (Anti-Obesity Agents) OR (Intensive medical)) AND (obesity) → 1772.

Data extraction

The data for each study was extracted independently by two authors. Disagreements were resolved by consensus. If no consensus was reached, a third author was consulted. Data extraction was carried out using the Rayyan tool— https://rayyan.qcri.org/ 13 .

All studies were analyzed by their titles and abstracts, according to inclusion and exclusion criteria. If the eligibility criteria was met, the full text would be extracted. All studies eligible for qualitative analysis are described in the “Results” section.

Missing data was clarified by contacting the authors directly.

Data validation

The risk of bias for intervention-type studies was analyzed using the guidelines of the Cochrane Back Review Group (CBRG) 14 .

Statistical analysis

As several studies of sufficient quality were available, a meta-analysis was carried out with measures of heterogeneity and publication bias. The data was presented through forest-plots, according to their statistical relevance.

Characteristics of study participants are presented as means, minimum and maximum values for quantitative variables, and as frequencies and percentages for qualitative variables. The prevalence values and 95% confidence intervals was calculated using the Wilson method To assess the global heterogeneity between the studies, Cochran's Q test was calculated, as well as the I2 (percentage of variation). The results of the studies' association measures and their respective 95% confidence intervals are presented in forest-plots.

Statistical analysis were performed using the Stata/MP 14.0 software for Windows.

Study selection

The electronic search found 9528 results for the keywords used. After removing 2809 duplicates and screening through abstract, we considered 55 potentially eligible studies for full-text analysis. Of these, 49 did not respect the exclusion criteria. Only 6 studies were considered eligible for qualitative analysis and 6 articles were eligible for meta-analysis [Fig.  1 ].

PRISMA 2020 flow diagram for new systematic reviews.

Many studies were excluded due to lack of description for the intervention in the non-surgical group.

Study characteristics

The following articles were included in the systematic review and meta-analysis 15 , 16 , 17 , 18 , 19 , 20 . In total, there were 427 participants. All studies were RCT. Four had a follow up of five years 15 , 16 , 19 and two had a follow up of 10 years 17 , 18 . Of the six eligible studies, two were undertaken in the United States of America 15 , 16 , two in Italy 17 , 19 , one in Australia 18 , and one in Singapore 20 . Study characteristics and detailed demographics can be found in Tables 1 and 2 . All studies included a group treated exclusively with intensive medical treatment (IMT). The definition of IMT differed between them but were considered if the patients had frequent follow up visits and were instructed on health habits including exercise and diet, with or without the use of pharmacological treatment.

There were four modalities of surgery used for weight loss: Roux-en-Y Gastric Bypass (RYGB) 15 , 17 , 18 , 19 , 20 ; Biliopancreatic diversion (BPD) 17 , 19 ; Laparoscopic Sleeve Gastrectomy (LSG) 15 , 16 ; Laparoscopic Adjustable Gastric Band (LAGB) 18 . The subgroup analysis for outcomes separated studies in RYGB, LSG and other types of surgery. The non-surgical treatment for obesity included one or the combination of the following medications: Orlistat, Phentermine, Naltrexone, Bupropion, Liraglutide, Lorcaserin, Sibutramine.

Risk of bias

After reading the articles included in the systematic review, the following elements were analyzed to determine the level of evidence: study design and selection, detection, loss, reporting and information bias. The summary of the risk of bias analysis for each of the included articles is presented in Fig.  2

Risk of bias analysis.

All studies had a low risk of bias for most criteria. In three of the studies, assessors were aware of the intervention received by study participants or the information was not available 16 , 17 , 20 . Three other studies 15 , 18 , 19 had bias regarding deviations from intended interventions due to the fact that an appropriate analysis to estimate the effects of assignment to intervention was not performed 15 ; patients assigned to the control group crossed over to the intervention group, and no measures were reportedly taken to balance that deviation 19 ; there was a significant loss of follow-up for all groups 20 .

All six studies had data on weight loss after treatment. Mean difference values and their respective 95% confidence intervals (95% CI) were calculated. In Fig.  3 A, the forest plot is shown. All publications found that surgical procedures were more efficient for long term weight loss. The global MD value was − 22.1 kg (95% CI [− 28.9; − 15.2). The measure of heterogeneity I2 (Higgins heterogeneity measure) was 77.8%, a value considered as high heterogeneity. According to Cochran’s Q heterogeneity test, the sample evidence did allow us to reject the null hypothesis of non-heterogeneity ( p  = 0.01).The subgroup analysis showed that there was not a significant difference between the types of surgery ( p  = 0.30).

(A ) Weight outcomes; ( B ) Waist circumference outcomes; ( C ) BMI outcomes.

Waist circumference

Four studies had data on waist circumference 16 , 17 , 19 , 20 . In Fig.  3 B, the forest plot is shown. Patients treated with surgery had a mean difference of − 12.3 (95% CI [− 15.0; − 9.6]) compared to IMT. The measure of heterogeneity I2 (Higgins heterogeneity measure) was 0%, a value considered as low heterogeneity. According to Cochran’s Q heterogeneity test, the sample evidence did not allow us to reject the null hypothesis of non-heterogeneity ( p  = 0.99).

The subgroup analysis showed that there was not a significant difference between the types of surgery ( p  = 0.99).

Five studies had data on BMI 16 , 17 , 18 , 19 , 20 . In Fig.  3 C, the forest plot is shown. Patients treated with surgery had a mean difference of − 8.0 (95% CI [− 10.5; − 5.5]) compared to IMT. The measure of heterogeneity I2 (Higgins’s heterogeneity measure) was 84%, a value considered high heterogeneity. According to Cochran’s Q heterogeneity test, the sample evidence did allow us to reject the null hypothesis of non-heterogeneity ( p  = 0.01).

The subgroup analysis showed that there was a significant difference between the types of surgery ( p  = 0.01). The group with LAGB and BPD surgery had the highest decrease in BMI, with a mean of − 10.0.

Triglycerides

Three studies had data on tryglycerides 17 , 19 , 20 . In Fig.  4 A, the forest plot is shown. Patients treated with surgery had a mean difference of − 0.7 (95% CI [− 0.8; − 0.6]) compared to IMT. The measure of heterogeneity I2 (Higgins’s heterogeneity measure) was 50.4%, a value considered high heterogeneity. According to Cochran’s Q heterogeneity test, the sample evidence did not allow us to reject the null hypothesis of non-heterogeneity ( p  = 0.08).

(A ) Triglycerides outcomes; ( B ) LDL outcomes; ( C ) HDL outcome; ( D ) Cholesterol outcomes.

The subgroup analysis showed that there was a significant difference between the types of surgery ( p  = 0.01), with a worse outcome for RYGB.

Four studies had data on LDL 16 , 17 , 19 , 20 . In Fig.  4 B, the forest plot is shown. Patients treated with surgery had a mean difference of − 0.5 (95% CI [− 1.0; 0.0]) compared to IMT. The measure of heterogeneity I2 (Higgins’s heterogeneity measure) was 92.7%, a value considered high heterogeneity. According to Cochran’s Q heterogeneity test, the sample evidence did allow us to reject the null hypothesis of non-heterogeneity ( p  = 0.01).

The subgroup analysis showed that there was a significant difference between the types of surgery ( p  = 0.01). There was an increase of 0.5 in LDL for the LSG group. The group with LAGB and BPD surgery had the highest decrease in LDL, with a mean of − 1.3.

Four studies had data on HDL 16 , 17 , 19 , 20 . In Fig.  4 C, the forest plot is shown. Patients treated with surgery had a mean difference of 0.1 (95% CI [0.0; 0.2]) compared to IMT. The measure of heterogeneity I2 (Higgins’s heterogeneity measure) was 90.5%, a value considered high heterogeneity. According to Cochran’s Q heterogeneity test, the sample evidence did allow us to reject the null hypothesis of non-heterogeneity ( p  = 0.01).

The subgroup analysis showed that there was a significant difference between the types of surgery ( p  = 0.01). The group with RYGB surgery had the highest significant increase in HDL, with a mean of 0.2.

Cholesterol

Three studies had data on cholesterol 17 , 19 , 20 . In Fig.  4 D, the forest plot is shown. Patients treated with surgery had a mean difference of − 0.9 (95% CI [− 1.6; − 0.2]) compared to IMT. The measure of heterogeneity I2 (Higgins’s heterogeneity measure) was 94.8%, a value considered as high heterogeneity. According to Cochran’s Q heterogeneity test, the sample evidence did allow us to reject the null hypothesis of non-heterogeneity ( p  = 0.01).

The subgroup analysis showed that there was a significant difference between the types of surgery ( p  = 0.01). The group with LAGB and BPD surgery had the highest decrease in cholesterol, with a mean of − 1.7.

Cardiovascular risk

Two studies had data on cardiovascular risk 17 , 19 . In Fig.  5 A, the forest plot is shown. Patients treated with surgery had a mean difference of − 0.08 (95% CI [− 0.10; − 0.05]) compared to IMT. The measure of heterogeneity I2 (Higgins’s heterogeneity measure) was 0%, a value considered as low heterogeneity. According to Cochran’s Q heterogeneity test, the sample evidence did not allow us to reject the null hypothesis of non-heterogeneity ( p  = 0.44).

(A ) Cardiovascular risk outcomes; ( B ) Systolic blood pressure outcomes; ( C ) Diastolic blood pressure outcomes; ( D ) HOMA outcomes; ( E ) Glycated Hemoglobin outcomes.

The subgroup analysis showed that there was no significant difference between the types of surgery ( p  = 0.36).

Systolic blood pressure

Four studies had data on systolic blood pressure 16 , 17 , 19 , 20 . In Fig.  5 B, the forest plot is shown. Patients treated with surgery had a mean difference of − 4.49 (95% CI [− 7.65; − 1.33]) compared to IMT. The measure of heterogeneity I2 (Higgins’s heterogeneity measure) was 71%, a value considered as high heterogeneity. According to Cochran’s Q heterogeneity test, the sample evidence did allow us to reject the null hypothesis of non-heterogeneity ( p  = 0.01).

The subgroup analysis showed that there was not a significant difference between the types of surgery ( p  = 0.79).

Diastolic blood pressure

Four studies had data on diastolic blood pressure 16 , 17 , 19 , 20 . In Fig.  5 C, the forest plot is shown. Patients treated with surgery had a mean difference of − 2.28 (95% CI [− 4.25; − 0.31]) compared to IMT. The measure of heterogeneity I2 (Higgins’s heterogeneity measure) was 60.5%, a value considered as high heterogeneity. According to Cochran’s Q heterogeneity test, the sample evidence did allow us to reject the null hypothesis of non-heterogeneity ( p  = 0.01).

The subgroup analysis showed that there was not a significant difference between the types of surgery ( p  = 0.66).

Three studies had data on HOMA 15 , 17 , 19 . In Fig.  5 D, the forest plot is shown. Patients treated with surgery had a mean difference of − 2.94 (95% CI [− 3.52; − 2.35]) compared to IMT. The measure of heterogeneity I2 (Higgins’s heterogeneity measure) was 14%, a value considered as low heterogeneity. According to Cochran’s Q heterogeneity test, the sample evidence did not allow us to reject the null hypothesis of non-heterogeneity ( p  = 0.32).

The subgroup analysis showed that there was no significant difference between the types of surgery ( p  = 0.33).

Glycated Hemoglobin

Five studies had data on glycated haemoglobin 15 , 16 , 17 , 19 , 20 . In Fig.  5 E, the forest plot is shown. Patients treated with surgery had a mean difference of − 1.0(95% CI [− 1.3; − 0.6]) compared to IMT. The measure of heterogeneity I2 (Higgins’s heterogeneity measure) was 79.8%, a value considered as high heterogeneity. According to Cochran’s Q heterogeneity test, the sample evidence did allow us to reject the null hypothesis of non-heterogeneity ( p  = 0.01).

The subgroup analysis showed that there was no significant difference between the types of surgery ( p  = 0.98).

Obesity is defined as a BMI greater than or equal to 30 by the CDC and is currently among the most prevalent diseases in the world, in addition to being an important risk factor for many other diseases. It has high rates of morbidity and mortality 21 , 22 and, in this context, weight loss can bring countless positive impacts to the individual. Currently, there are several treatments for obesity, and we can divide them into non-surgical or surgical.

Non-surgical treatments include non-drug and drug treatments. Among the non-medicated, we can highlight the change in eating habits, regular physical exercise, and cognitive behavioral therapy 8 . Ideally, these measures should be implemented for all patients living with obesity, even for those who will undergo drug or surgical treatment. Recently, in addition to lifestyle change, neuromodulation with deep transcranial stimulation has also been studied and has shown effectiveness in weight loss reduction 23 .

A systematic review carried out in 2021, which analyzed 64 articles concluded that among the most effective non-surgical interventions are low-carbohydrate or low-fat diets and combined therapies. This study also showed that non-drug interventions, such as physical exercise, when used alone, are not very effective in reducing the weight of these patients Therefore, a combination of two or more therapies should be chosen 24 .

Pharmacological treatment must be chosen together with the patient. One or more drugs can be used, the main ones used being: Liraglutide, Semaglutide, Tirzepatide, Orlistat, Phentermine and Sibutramine 25 .

Liraglutide was recently approved for the treatment of obesity and is now one of the most widely used drugs. It acts as a GLP-1 receptor agonist 26 , 27 , 28 , enhancing its effects. This group of drugs is already known in the treatment of Type 2 Diabetes Mellitus, a condition that can often be associated with obesity 29 , 30 , since its pathophysiology involves increased insulin resistance. The main actions of this drug are: increased satiety due to a reduction in the speed of gastric emptying, increased insulin release and decreased glucagon release. Semaglutide is a drug with a similar mechanism of action who demonstrated not only a substantial weight loss 31 , but was also associated with a lower 10-year T2D risk in people with overweight or obesity after 2 years of follow up 32 . More recently, a new drug that combines GLP-1 and GIP receptor agonist, Tirzepatide, has shown even better results in the short term 33 .

Orlistat, in turn, reversibly inhibits the lipase enzyme 34 , which has the function of breaking down fat from food for its absorption, as well as inhibiting the absorption of ingested triglycerides. Thus, there is elimination of fat in the feces 35 . The main adverse effects are gastrointestinal symptoms, however this can be beneficial as it leads to a change in behavior, for example causing a lower consumption of foods rich in fat 36 .

Phentermine, an amphetamine analogue, can be used in conjunction with topiramate for the treatment of obesity. The mechanism of action of the drugs is not yet known, however, significant weight loss has already been observed, in addition to a reduction in the consumption of hypercaloric foods and a decrease in the speed of gastric emptying with the use of this combination of drugs 37 , 38 .

Sibutramine, widely used in the 1990s, acts to inhibit the reuptake of serotonin, norepinephrine, and dopamine 34 . Serotonin, in turn, activates POMC system neurons and inhibits NPY neurons, thereby promoting reduced appetite and increased satiety. Despite generating weight reduction 39 , some data show increased cardiovascular risk 40 , and therefore, it is no longer used as a first-line drug.

Among the possible surgeries, the most performed today are: Roux-en-Y Gastric Bypass (RYGB), Biliopancreatic diversion (BPD), Laparoscopic Sleeve Gastrectomy (LSG) and Laparoscopic Adjustable Gastric Band (LAGB). According to the NIH and the American Bariatric Society 41 , 42 , some indications for performing bariatric surgery are adults with BMI greater than or equal to 40 and adults with BMI greater than 35 accompanied by some comorbidity such as type 2 diabetes mellitus, obstructive sleep apnea or hypertension.

RYGB is one of the best-known procedures and its complications vary according to the surgical technique used. Some complications include gastric distention, ulcers, cholelithiasis, hernias, dumping syndrome, and hyperammonaemia encephalopathy.

BPD presents long-term nutritional complications, such as anemia, bone diseases and fat-soluble vitamin deficiency. This technique has high mortality rates, mainly due to the complexity of the technique.

Among the procedures described, LSG is the one with the fewest complications, being described in the literature bleeding or stenosis of the stoma. An alternative technique using endoscopy for sleeve gastroplasty has shown to be safe and efficient for weight loss after 104 weeks, with important improvements in metabolic comorbidities 43 .

The procedure with the lowest mortality rate is the LAGB 44 . Despite this, it can present complications such as obstruction, band erosion, band slippage and gastric prolapse, esophagitis, hernia, in addition to having a high rate of reoperation, reaching 50% of patients who underwent this surgery 45 .

In this article, we compare data on weight loss through intensive drug treatment, which includes changes in eating habits, physical exercise, and medications, and through surgical treatment. Both treatments showed that weight loss caused an improvement in the lipid panel, with a reduction in total cholesterol, triglycerides and LDL, an increase in HDL, improvement in systolic and diastolic blood pressure, decrease in glycated hemoglobin and insulin resistance (accessed through HOMA), in addition to reducing the risk for cardiovascular diseases.

Our systematic review confirmed the findings of individual studies that bariatric surgery has a greater potential for weight reduction, BMI and waist circumference, as already described in individual articles and widely in the literature. It should be noted that even in the long term, this difference remained. Similarly, a 2014 Cochrane systematic review 46 comparing RCT with more than 1 year of follow-up showed that all 7 articles included demonstrated an advantage of the surgical group. An article 47 on the use of pharmacological treatment for obesity showed that even recent drugs approved, including GLP 1 agonists, are not able to reduce weight to levels similar to those of bariatric surgery to date, despite the emergence of new drugs still in initial phase 48 . It is worth mentioning that in these studies the comparison time is relatively short (12 months) and that we do not have data on the long-term impact. Thus, in relation to long term weight loss, bariatric surgery is still the best option.

Most articles were not able to individually demonstrate that surgical treatment is superior to non-surgical in terms of pressure reduction. However, the result of the meta-analysis showed a superiority of the surgical group in relation to both systolic and diastolic pressure, more pronounced in the BPD group. Wang 49 performed a systematic review focused on the impact on pressure and demonstrated that there was a reduction in systolic and diastolic values, but the subgroup analysis showed that this occurs only in the RYGB groups for systolic pressure. Similarly, Schiavon also demonstrated a significant reduction in the need of blood pressure medication after 3 years in the RYGB group when compared intensive medical treatment for obesity 50 . This difference found in only one subtype of surgery seems to be just a reflection of the sample size, which can be interpreted that surgical treatment in general tends to reduce pressure to a greater extent than non-surgical treatment. The fact that different types of surgery are significant may reflect the studies selected in our meta-analysis, which have longer follow-ups.

In relation to both HOMA-IR and glycated Hb, there was a more significant improvement in the group that underwent surgery. The way in which the data on diabetes remission was reported in the articles did not allow a meta-analysis to be carried out with these data and, therefore, it was not included. However, individual data from the Mingrone 2015, Mingrone 2021 and Schauer articles showed that the surgery group had better results. A network meta-analysis from 2021 51 comparing the different types of metabolic surgery for the treatment of obesity and diabetes showed that RYGB was 20% more likely to result in remission of type 2 diabetes compared to SG. There was no significant difference between the other groups. Moreover, the effects of bariatric surgery on diabetes is not exclusive for patients with obesity, as shown by a study with patients with a BMI of 27–32 kg/m 2 that had a better glycemic control when treated with RYGB 20 . Regarding the lipid profile, Schauer's study was not able to demonstrate superiority in relation to LDL and HDL parameters. However, by combining the data from Mingrone's articles, it is possible to demonstrate that surgical treatment is superior. Regarding cholesterol reduction, Mingrone's studies showed that although RYGB and BDP were better in relation to non-surgical treatment, the BDP technique had a statistically greater reduction in relation to RYGB. This can be explained by the greater intestinal exclusion in BDP and, therefore, having a greater impact on lipid absorption. Despite Sayeed's study 52 et al. was not included in this meta-analysis due to the inadequate way of separating the groups for analysis, the results regarding the lipid profile showed that the group that received both interventions was superior to the exclusive non-surgical treatment. It is important to point out that despite a statistically significant difference between the groups, the effect size of this difference is probably not clinically significant.

The choice of treatment for obesity can also have an impact on several other patient comorbidities. Hossain et al. 53 performed a systematic review with 26 studies that showed that bariatric surgery appears to be more effective in the treatment of asthma. Similarly, a study by Crawford et al. 15 showed that there is a greater increase in bone turnover in groups undergoing bariatric surgery in relation to pharmacological treatment. Other than that, bariatric surgery is also demonstrated to be superior in the treatment of other obesity related pathologies, such as Non-Alcoholic Steatohepatitis (NASH), and in the treatment of obesity in adolescents 54 , 55 .

The effect of major cardiovascular adverse events (MACE) and mortality 56 have also been promising for bariatric surgery. A recent cohort comparing bariatric surgery in patients with obesity and use of GLP1-agonists inpatients with diabetes showed a lower risk of MACE in the surgical group 57 . The surgical treatment has also shown superiority when compared to medical treatment regarding the prevention of diabetic kidney disease in 5 years for patients with diabetes and obesity 58 . Boyers et al. evaluated the cost-effectiveness of surgical and pharmacological treatment in the treatment of obesity and found that RYGB should be the treatment of choice only if the optimization of health system costs is considered 59 .

Another important consideration is the fact that pharmacological and surgical treatment for obesity are not mutually exclusive. Most clinicians choose to combine both treatment modalities in practice to improve results. Weight gain after bariatric surgery is a known possibility, and for those patients, two-thirds of the weight regain can be safely lost with GLP1 agonist, providing clinicians with a therapeutic option for this clinical challenge.

Methodologies and limitations of the studies

Despite the large number of articles in the literature on the treatment of obesity, there are few RCTs comparing non-surgical and surgical treatment, and most of them only follow up in the short term. In addition, many articles do not adequately describe the strategy used in non-surgical treatment. This lack of data and standardization in this type of treatment can lead to bias and possibly the formation of extremely heterogeneous groups for analysis.

Most of the studies included in our systematic review have diabetes as an inclusion criteria. In this circumstance, our findings may not be generalized to patients with obesity without diabetes.

Another important limitation of our systematic review refers to pharmacological treatment in the non-surgical group. The use of GLP 1 agonists has great potential in the treatment of obesity, but they have only started to be used recently. As the purpose of our article is to assess the long-term impact, there are still few articles available that used this drug. The use of the most recent medications, such as Tirzepatide, could not be evaluated in our study, once there are no RCTs in the literature presenting its long-term effects. Those drugs proved to be very efficient and might have similar effect in the long term. Future systematic reviews may reveal a different results when including the new generation of weight loss medication.

Finally, choosing the most appropriate treatment often involves individual characteristics of each patient, and the impact on quality of life can be extremely subjective and difficult to assess.

Obesity is a disease that increases the morbidity and mortality of patients, contributing to several secondary diseases. This systematic review evaluated the impact on the main variables related to obesity in the long term. The findings indicated that both treatment modalities are efficacious in managing obesity; however, the surgical group demonstrated superior outcomes in comparison to the non-surgical group across most variables. Nonetheless, the advent of novel pharmacological treatments has shown promising potential. Further studies focusing on the long-term impacts of these new drug treatments should be undertaken to allow for a comprehensive comparison with non-surgical treatment methods.

Data availability

Data is provided within the manuscript or supplementary information files.

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Conceptualization: L.Z.P., A.M. Methodology: L.Z.P., L.R.I., A.M. Formal analysis: L.Z.P., R.F.V.N., A.M. Data Curation: L.Z.P., W.A.F.B., R.M.N., V.S.C., A.S.C., J.V.T., R.F.V.N., M.O.S., F.S.N., V.C.M. Writing—Original Draft: L.Z.P., W.A.F.B., R.M.N., V.S.C., A.S.C., J.V.T., R.F.V.N., M.O.S., F.S.N., V.C.M. Writing—Review and Editing: L.Z.P., R.F.V.N., L.R.I., W.T.H., L.A.C., A.M., W.A. Visualization: L.Z.P., R.F.V.N., A.M. Supervision: L.R.I., W.T.H., L.A.C., A.M., W.A. Project administration: L.R.I., W.T.H., L.A.C., A.M., W.A.

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A scoping review of academic and grey literature on migrant health research conducted in Scotland

• G. Petrie 1 ,
• K. Angus 2 &
• R. O’Donnell 2  

BMC Public Health volume  24 , Article number:  1156 ( 2024 ) Cite this article

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Migration to Scotland has increased since 2002 with an increase in European residents and participation in the Asylum dispersal scheme. Scotland has become more ethnically diverse, and 10% of the current population were born abroad. Migration and ethnicity are determinants of health, and information on the health status of migrants to Scotland and their access to and barriers to care facilitates the planning and delivery of equitable health services. This study aimed to scope existing peer-reviewed research and grey literature to identify gaps in evidence regarding the health of migrants in Scotland.

A scoping review on the health of migrants in Scotland was carried out for dates January 2002 to March 2023, inclusive of peer-reviewed journals and grey literature. CINAHL/ Web of Science/SocIndex and Medline databases were systematically searched along with government and third-sector websites. The searches identified 2166 journal articles and 170 grey literature documents for screening. Included articles were categorised according to the World Health Organisation’s 2016 Strategy and Action Plan for Refugee and Migrant Health in the European region. This approach builds on a previously published literature review on Migrant Health in the Republic of Ireland.

Seventy-one peer reviewed journal articles and 29 grey literature documents were included in the review. 66% were carried out from 2013 onwards and the majority focused on asylum seekers or unspecified migrant groups. Most research identified was on the World Health Organisation’s strategic areas of right to health of refugees, social determinants of health and public health planning and strengthening health systems. There were fewer studies on the strategic areas of frameworks for collaborative action, preventing communicable disease, preventing non-communicable disease, health screening and assessment and improving health information and communication.

While research on migrant health in Scotland has increased in recent years significant gaps remain. Future priorities should include studies of undocumented migrants, migrant workers, and additional research is required on the issue of improving health information and communication.

Peer Review reports

The term migrant is defined by the International Organisation for Migration as “ a person who moves away from his or her place of usual residence, whether within a country or across an international border, temporarily or permanently, and for a variety of reasons. The term includes several well-defined legal categories of people, including migrant workers; persons whose particular types of movements are legally-defined, such as smuggled migrants; as well as those whose status are not specifically defined under international law, such as international students.” [ 1 ] Internationally there are an estimated 281 million migrants – 3.6% of the world population, including 26.4 million refugees and 4.1 million asylum seekers – the highest number ever recorded [ 2 ]. The UN Refugee Society defines the term refugee as “ someone who has been forced to flee his or her country because of persecution, war or violence…most likely, they cannot return home or are afraid to do so .” The term asylum-seeker is defined as “someone whose request for sanctuary has yet to be processed.” [ 3 ].

Net-migration to Europe was negative in the 19th century due to higher levels of emigration, however in the mid-20th century immigration began to rise, because of an increase in migrant workers and following conflicts in the Middle East and North Africa [ 4 ]. Current migration drivers include conflicts alongside world-wide economic instability, exacerbated by the Covid-19 pandemic [ 5 ]. Environmental damage due to climate change is expected to inflate the number of asylum seekers entering Europe in future [ 6 ]. The increase in migration to Europe is not a short-term influx but a long-term phenomenon, and European nations must adapt and find solutions to resulting financial, safeguarding and health challenges [ 7 ].

Data on healthcare use by migrants in Europe is variable, which means cross-country comparisons are inadequate [ 8 ]. Many countries do not record migration information within health records and all use disparate criteria to classify migrant status. The lack of comparative data hinders public health surveillance and effective interventions [ 9 ]. Even where information is available, results can be contradictory due to the multifarious migrant population. Migrants have a wide range of origin countries, socio-economic position, age and journeys undertaken which can affect health status [ 10 ].

Migrants initially may have better health than the general population, known as the ‘Healthy Migrant effect’ [ 11 ]. However, health declines with increasing length of residence [ 12 ] and over time to levels comparable with the general population [ 13 ]. Second generation immigrants may have higher mortality than average [ 14 ]. The process of acculturation to the host country, with adoption of unhealthy lifestyle and behaviours, increases the risk for chronic disease [ 15 ]. In addition, inequalities in health of migrants compared to host populations has been confirmed by wide-ranging research [ 16 ].

Host countries may limit healthcare access, with undocumented migrants sometimes only entitled to emergency care [ 17 ]. Even when access is granted, inequitable services can affect quality of care due to language barriers and cultural factors [ 18 ]. Poor working/living conditions and discrimination can exacerbate health inequalities [ 12 ]. Processing facilities for asylum seekers are frequently overpopulated, stressful environments [ 19 ] and threat of deportation, lack of citizenship rights and integration can negatively affect health and access to care [ 20 ]. Undocumented workers are unprotected by health and safety legislation leading to dangerous working conditions and injuries [ 15 ].

A systematic review of migrant health in the European Union (EU) found migrants have worse self-perceived health than the general population [ 21 ]. Research evidence indicates increased prevalence of cardiovascular disease, diabetes, mental health disorders and adverse pregnancy outcomes. Exposure to conflict, harsh travel conditions and suboptimal vaccine programmes can mean higher risk of communicable disease [ 22 ]. Scoping reviews have also been conducted to describe trends within migration health research in the United Kingdom (UK) [ 23 ] and identify gaps for future research agendas in the UK [ 23 ] and in the Republic of Ireland [ 24 ].

Almost three-quarters (73%) of published migration health research in the UK has been conducted in England, focusing primarily on infectious diseases and mental health. There is limited evidence on the social determinants of health, access to and use of healthcare and structural and behavioural factors behaviours that influence migrant health in the UK [ 23 ]. By contrast, a large amount of the migration research conducted in the Republic of Ireland has focused on the social determinants of health, and on health system adaptations, with a paucity of research focusing on improving health information systems [ 24 ].

Migration and Health in Scotland

Immigration to Scotland began to rise in 2003 with the expansion of the EU [ 25 ]. The population in Scotland increased from 5.11 million to 5.47 million between 2005 and 2020 and is predicted to continue rising until 2028 [ 26 ] despite low birth rates, with the increased population resulting from inward migration [ 27 ]. Scotland’s population is becoming more ethnically diverse [ 28 ] and susceptibility to different health conditions varies by ethnic group, which has implications for the planning and provision of health services [ 29 ]. 7% of the current Scottish population are non-UK nationals and 10% were born outside Britain. The commonest countries of origin were Poland, Ireland, Italy, Nigeria and India [ 30 ].

Within Scotland, linking health data to ethnicity is standard in order to monitor and improve health of minority groups [ 31 ]. Ethnic background can differ from country of birth which means migration status cannot be assumed [ 32 ], although health inequalities experienced by migrants often extend to affect all ethnic minority groups [ 33 ]. The Scottish Health and Ethnicity Linkage Study (SHELS) linked census data to health records of 91% of the population which has provided information on mortality and morbidity by ethnic group and country of birth [ 34 ]. SHELS research indicates that the white-Scottish population have a higher mortality rate than other ethnic groups. This may be consequent to the comparatively poor health of the Scottish population relative to other European nations: high mortality rates in the general population may cause a perception that the health of minorities is more advantageous than in reality [ 35 ].

Cezard et al’s [ 13 ] analysis of self-perceived health among people in Scotland found that being born abroad had a positive impact on health status. Health declined with increased length of residence, which may be explained by cultural convergence with the majority population. Allik et al. [ 36 ] compared health inequalities by ethnic background and found that with increasing age, health differences reduced thus people aged over 75 of all ethnicities had similar or worse health status than White-Scottish people. While working-age migrants appear to be healthier than the White Scottish population, it cannot be assumed that in future this would extend to older age groups.

Research has shown deprivation as a cause of heath inequalities among ethnic minority and migrant groups [ 37 ]. The socio-economic status of minority ethnic groups in Scotland is unusual, as most are of similar or higher status than the white-Scottish population [ 38 ]. Therefore, public health interventions targeting deprivation may not address risk-factors for ethnic minorities and migrants [ 36 ]. Further research on determinants of health in migrants can help with planning and design of inclusive policies.

The 2011 census indicated that 50% of immigrants lived in the cities of Edinburgh, Glasgow, and Aberdeen. Glasgow had a greater percentage of non-European immigrants due to participation in the Asylum dispersal programme [ 39 ]. 10% of UK asylum seekers are placed in Glasgow, but records are not kept following approval of asylum claims, therefore the size of the refugee population is unknown [ 40 ]. While immigration is controlled by the British government, in policy areas devolved to the Scottish government, refugees and asylum seekers have more rights than elsewhere in UK, including access to primary healthcare for undocumented migrants [ 40 ]. Despite the mitigating effect of Scottish policies, asylum seekers’ health is worsened by the asylum process and associated poverty, marginalisation, and discrimination [ 40 ]. Health deteriorates with increasing length of time in the asylum system [ 40 ] and asylum seekers and refugees have additional health needs and require enhanced support [ 41 ]. Research on the health needs of asylum seekers in Scotland is required to ensure adequate healthcare.

Aim and objectives

While scoping reviews on migrant health have been carried out in Europe [ 12 ], Ireland [ 24 ] and the UK [ 23 ] none are currently specific to the Scottish context. Given the devolved government of Scotland and demographics described above, a targeted review would help to clarify research priorities, with the aim of improving health and health care within the migrant community in Scotland. This work therefore builds on the published scoping review of migrant health in the Republic of Ireland [ 24 ]. The authors recommend replication of the study in other countries to facilitate cross-country comparison. Our aim was to scope peer-reviewed research and grey literature on migrant health conducted in Scotland and identify any gaps in the evidence. Our objectives were to: [1] understand the extent of the available research by topic area [2] summarise the types of research already conducted, populations studied, topics covered and approaches taken [3], map the existing research conducted in Scotland and [4] identify areas for future research based on any gaps in the evidence identified.

A scoping review was conducted as they can aid detection of evidence gaps [ 42 ] and allow incorporation of grey literature in topics with insufficient published research [ 43 ]. Arksey and O’Malley’s [ 44 ] five stage scoping review framework was used.

Stage 1: identifying the research question

Arskey and O’Malley [ 44 ] suggest maintaining a broad approach to identifying the research question, in order to generate breadth of coverage. On this basis, and in line with the research question identified in the Villarroel et al. [ 24 ] scoping review, our research question was framed as follows: What is the scope, main topics and gaps in evidence in the existing literature on health of international migrants living in Scotland? Arksey and O’Malley [ 44 ] highlight the importance of defining terminology at the outset of scoping reviews. For consistency, we used the broad definition of ‘migrant’ as per Villaroel et al. [ 24 ], from the International Organisation for Migration (IOM) [ 1 ]. References to refugees or asylum seekers followed the United Nations Refugee Agency definitions [ 3 ].

Stage 2: identifying relevant studies

Electronic database searches identified reports alongside a grey literature search, in line with Arskey and O’Malley’s [ 44 ] guidance to search for evidence via different sources. CINAHL, Web of Science, SocIndex and Medline academic databases were selected with input from co-authors. Search terms for the review were based upon those used by Villaroel et al. [ 24 ] with additional relevant terms from Hannigan et al. [ 9 ] The strategy combined three sets of terms for: Migrants (e.g., refugee, migrant, immigrant or newcomer), Scotland and Health. Both free text terms and index terms were used and adapted to the 4 academic databases and searches were run on 10th March 2023 (see Additional File 1 for database search strategies). Thirteen Government, University, and third-sector websites in Scotland were scoped for selection then hand-searched for grey literature (listed in Additional File 1 ).

Stage 3: study selection

Net-migration to Scotland increased in the 2000s [ 27 ] hence a date range of January 2002-March 2023 was used to identify evidence. The search was limited to English only. Inclusion/exclusion criteria for the studies were based on those used by Villaroel et al. [ 24 ] and expanded upon following discussion with co-authors (see Table  1 ). Reports were included if based on primary or secondary research on the health of international migrants in Scotland and used qualitative, quantitative or mixed methods research design. International or UK based reports were only included if Scottish results were documented separately. Reports on the health of ethnic minority groups in Scotland was included if place of birth was recorded. Research on internal (non-international) migrants within Scotland, either moving from one Scottish area to another or from another part of the United Kingdom to Scotland, were excluded.

Stage 4: data charting

All records were saved to RefWorks for screening. Records were first screened at title/abstract stage with 10% independently checked by the co-authors. The remaining reports were single screened using full text by the first author. Data from the included records was extracted and organised in tabular form under the following headings, which were agreed by team members: article type (peer-reviewed article or grey literature), publication date, geographical setting, study/intervention’s target population, funding, primary research focus on migrant health (y/n), study objective, data collection method, study design (qualitative/quantitative/mixed) and main finding. Reports were not critically appraised in this scoping review.

Stage 5: collating, summarising and reporting results

A report (either a peer-reviewed journal article or grey literature report) is used as our unit of analysis. In order to present the range of research identified, reports were grouped by the different headings in our data charting table and the outcomes considered for relevance to our scoping review’s aim. Our Results summarise the recency, focus, study designs and funding sources of the identified research, followed by the geographical settings and whether Scotland was included in international research reports. Reports were grouped by their study population and further sub-divided by publication type and geographical area for summarising. Finally, the WHO’s European strategy and action plan (SAAP) for refugee and migrant health [ 7 ] is a policy framework designed to help governments and other stakeholders monitor and improve migrant health in Europe. There are nine strategic areas in the WHO’s SAAP, which prioritise the most salient issues. In line with Villaroel et al’s [ 24 ] approach and in order to compare scoping review outcomes, these areas were used to categorise the findings of this review. Each report was matched to the most appropriate SAAP:

Establishing a Framework for Collaborative Action.

Advocating for the right to health of refugees.

Addressing the social determinants of health.

Achieving public health preparedness and ensuring an effective response.

Strengthening health systems and their resilience.

Preventing communicable disease.

Preventing and reducing the risks caused by non-communicable disease.

Ensuring ethical and effective health screening and assessment.

Improving health information and communication.

The primary focus (aims and objectives) of each report was used to identify the relevant SAAP area/areas. To improve reliability, results were compared using coding criteria used in Villaroel et al’s study (MacFarlane 2023, personal communication, 31st May). 10% of the reports were checked by one co-author to ensure consistent coding to SAAP categories. Any instances of uncertainty in mapping reports to the relevant SAAP area/areas were discussed and resolved by team members.

This scoping review of the literature on migrant health in Scotland identified 2166 records from academic literature databases, following duplicate removal, and 170 records from website searches (see Fig.  1 ). Following screening, a total of 71 peer-reviewed journal articles and 29 grey literature studies (totalling 100 reports) were included for analysis (Results table and reference list are presented in Additional File 2 ).

Flow chart illustrating the identification of sources of evidence included in the scoping review

Overall findings

The majority of reports were published between 2013 and 2022. Fifty-eight reports (58%) focused exclusively on migrant health [ 18 , 39 , 45 , 46 , 47 , 48 , 49 , 50 , 51 , 52 , 53 , 54 , 55 , 56 , 57 , 58 , 59 , 60 , 61 , 62 , 63 , 64 , 65 , 66 , 67 , 68 , 69 , 70 , 71 , 72 , 73 , 74 , 75 , 76 , 77 , 78 , 79 , 80 , 81 , 82 , 83 , 84 , 85 , 86 , 87 , 88 , 89 , 90 , 91 , 92 , 93 , 94 , 95 , 96 , 97 , 98 , 99 , 100 , 101 , 102 ]. 23 centred on health but included other populations in addition to migrants – for example research on ethnic minorities or other vulnerable groups [ 13 , 31 , 35 , 103 , 104 , 105 , 106 , 107 , 108 , 109 , 110 , 111 , 112 , 113 , 114 , 115 , 116 , 117 , 118 , 119 , 120 , 121 , 122 ]. Seventeen reports were included where the sample population were migrants, but the primary topic was not health – for example destitution, integration, and service needs [ 27 , 73 , 74 , 123 , 124 , 125 , 126 , 127 , 128 , 129 , 130 , 131 , 132 , 133 , 134 , 135 ]. Health data was reported as part of the wider subject matter. One report [ 136 ] looked at the social determinants of breastfeeding including migrant status and one [ 137 ] compared attitudes to aging and family support between countries.

Funding sources were not declared for 35 (35%) of reports. The Scottish Government funded 20 reports (20%) [ 13 , 27 , 32 , 39 , 45 , 46 , 47 , 66 , 77 , 88 , 99 , 100 , 101 , 102 , 113 , 116 , 119 , 121 , 129 , 134 ]. Other common sources of funding included Government funded public bodies ( n  = 13) [ 45 , 48 , 49 , 50 , 51 , 52 , 53 , 104 , 107 , 113 , 116 , 131 , 136 ], the Scottish Health Service ( n  = 18) (either the National Health Service (NHS) [ 13 , 54 , 56 , 57 , 58 , 59 , 102 , 113 , 116 ], local NHS trusts [ 45 , 60 , 61 , 77 , 102 , 103 , 112 ] or by Public Health Scotland [ 13 , 113 ]) Eleven reports (11%) were funded by Universities. The charity sector financed 15 (15%) reports [ 53 , 63 , 66 , 69 , 70 , 71 , 72 , 73 , 74 , 103 , 111 , 123 , 125 , 132 , 138 ] and the EU and Scottish local authorities funded four reports each [ 45 , 62 , 75 , 76 , 77 , 102 , 125 , 135 ]. Professional bodies financed one report [ 126 ] as did the Japanese government [ 64 ]. No reports received funding from the business sector. The biggest sources of funding for grey literature were Refugee charities (40%) and the Scottish government (30%) (see Fig. 2 ).

Sources of funding for migrant health research in Scotland

Research methods and data collection

52% of reports used qualitative research methods. Forty-five reports (86%) collected data using 1–1 interviews and 24 (46%) used focus groups. Other methods of data collection included questionnaires (six studies (11%)), workshops (two studies (3.85%)) and observation (two studies (3.85%)). Oral/written evidence, guided play sessions, family case studies and participatory activity sessions were used in one report each.

28% of reports used quantitative research methods, most commonly cross section design (ten studies (36%)) and cohort design (18 studies (64%)). Information was obtained from databases including medical records, Census data and national records in 21 reports (75%). Questionnaires were used in six reports (21%). Other methods including body measurements, food diaries, blood samples, interviews and case reviews were used in 1 report each.

20% of reports used mixed methods. The most common method of data collection was questionnaires in 14 reports (70%), interviews in ten reports (50%), focus groups in seven reports (35%), workshops in three reports (13.6%), and databases in three reports (13.6%). Other methods included literature review in two reports (10%), case note reviews in two reports (10%) and one reports each used mapping and school records.

Geographical areas of study

Ninety-one reports were situated in Scotland, of which 35 (38.5%) covered the whole country and 56 (61.5%) specified a city or area where research was undertaken. Some UK and international reports also specified the area of Scotland. The largest share of research within Scotland overall was in Glasgow with 36 reports, followed by Edinburgh with 16 reports, Lothian with six reports, Aberdeen with five reports and Grampian with three reports. The Northeast, Stirling, Highlands, Inverness, Lanarkshire, Motherwell and Selkirk had one report in each area.

There were seven international reports, three on mortality by country of birth [ 75 , 76 , 78 ], one on cross cultural communication [ 79 ], one on maternity care in Poland and Scotland [ 99 ], one comparing attitudes to aging in China and Scotland [ 137 ] and one on the link between birthweights and integration of migrants [ 64 ]. The remaining two reports were UK based, one on immunisation of Roma and traveller communities [ 117 ] and one on the link between ethnic diversity and mortality [ 104 ]. All the included international and UK reports documented the Scottish data separately within results.

Migrant population

Thirty-one reports included all migrants in the study population. The remaining reports included 30 studies on asylum seekers/refugees, 11 on Polish migrants, ten on Africans, six each on South Asians/Chinese/European, three on Arabs, and two on Roma populations (see Fig.  3 ). Most reports did not specify the country of origin for Asylum seekers and refugees - where country of birth was specified, reports were also included in the appropriate category.

Migrant populations studied in health research in Scotland

Grey literature and peer-reviewed reports differed in population focus. The most common populations of interest in grey literature were asylum seekers/refugees consisting of 18 reports (62%) [ 27 , 47 , 54 , 55 , 59 , 63 , 70 , 71 , 72 , 73 , 74 , 123 , 125 , 127 , 128 , 132 , 134 , 138 ] while for peer-reviewed journals 24 reports (34%) focused on all migrants [ 13 , 35 , 45 , 48 , 64 , 76 , 78 , 79 , 80 , 81 , 104 , 105 , 108 , 109 , 113 , 114 , 115 , 116 , 118 , 120 , 121 , 122 , 136 ].

Migrant study population also differed by local area; Glasgow city, where the majority of research occurred, had 18 reports of 36 (50%) on Asylum seekers/refugees [ 47 , 48 , 52 , 53 , 54 , 55 , 58 , 63 , 70 , 71 , 72 , 82 , 83 , 127 , 128 , 130 , 138 , 139 ] eight reports (22%) on Africans [ 52 , 53 , 84 , 85 , 86 , 87 , 106 , 107 ], seven reports (19%) on all migrants [ 45 , 48 , 80 , 102 , 104 , 105 , 121 ] and two reports (5.5%) on Roma migrants [ 103 , 117 ]. Other populations had one reports each. In Edinburgh five reports of 16 (31%) were on the Polish population [ 56 , 67 , 68 , 89 , 90 ], and two reports (12.5%) on Asylum seekers/refugees [ 60 , 133 ], Chinese [ 62 , 137 ], South Asian [ 46 , 119 ], all migrants [ 105 , 121 ] and Africans [ 87 , 107 ]. The remaining migrant groups had one report each. Other areas of Scotland show no clear pattern with studies in disparate migrant population groups.

Number of reports per Strategic and Action Plan (SAAP) Area

SAAP Area mapping

1. establishing a framework for collaborative action.

Nine reports had a primary focus on collaborative action and were categorised under SAAP area 1 (see Fig.  4 ) [ 66 , 70 , 72 , 73 , 103 , 125 , 129 , 132 , 134 ]. Four reports (33%) used a mixed methods study design, the remaining five reports (67%) used a qualitative design. One report [ 66 ] focused on the epidemiology of female genital mutilation and a proposed intervention strategy. One report [ 66 ] focused on the epidemiology of female genital mutilation and a proposed intervention strategy. One report [ 103 ] evaluated service provision to the Roma community in Glasgow. The remaining reports focused on refugees and asylum seekers: four [ 73 , 125 , 132 , 134 ] evaluations of refugee integration projects, one [ 70 ] on services available to pregnant women, and one [ 72 ] an assessment of a peer-education service. One report [ 129 ] was a review of service provisions for migrants during the Covid-19 pandemic. All reports in SAAP area 1 were grey literature and three (37.5%) had a primary focus on migrant health while four (50%) focused on integration, one (11%) included data on ethnic minorities and one (11%) on services during the covid-19 pandemic. The majority (seven reports (78%)) were also categorised to another SAAP area most commonly area 2 (five studies (55%)) or area 5 (four studies (44%)).

2. Advocating for the right to health of refugees

Nineteen reports focused on SAAP area 2, advocating for the right to health of refugees (see Fig.  4 ) [ 47 , 52 , 53 , 54 , 55 , 63 , 70 , 71 , 83 , 103 , 123 , 124 , 125 , 127 , 128 , 129 , 134 , 138 , 140 ]. Sixteen reports (84%) had a qualitative study design and the remaining three (16%) reports used mixed methods. Nine reports (47%) focused on the health impact of the asylum system [ 52 , 55 , 71 , 74 , 123 , 127 , 128 , 129 , 138 ], five (26%) on health and access to care [ 47 , 54 , 83 , 103 , 124 ], two (10.5%) on maternity care [ 63 , 70 ], two (10.5%) on integration services [ 125 , 134 ] and one report on mental health in HIV positive migrants [ 53 ]. Nine reports (47%) had a primary focus on migrant health while the remaining 10 (53%) also involved wider social issues. The majority (15 (79%)) of reports were grey literature. All the articles in this group overlapped with another SAAP area. Area 3 is the most common joint category with ten reports (53%) followed by area 5 with seven reports (37%), area 1 shares five reports (26%), while areas 4 and 8 share one report each (5%).

3. Addressing the social determinants of health

Twenty-nine reports were categorised to SAAP area 3 – addressing the social determinants of health (see Fig.  4 ) [ 13 , 27 , 45 , 50 , 52 , 55 , 60 , 62 , 63 , 65 , 68 , 71 , 74 , 80 , 81 , 82 , 91 , 92 , 93 , 102 , 112 , 123 , 124 , 127 , 128 , 136 , 137 , 138 ]. The majority (14 (48%)) used a qualitative study method, eight (28%) used quantitative methodology and the remaining seven reports (24%) used mixed methods. Nineteen reports (65.5%) were peer-reviewed journals [ 13 , 45 , 50 , 52 , 60 , 62 , 63 , 65 , 68 , 80 , 81 , 82 , 91 , 92 , 93 , 104 , 112 , 124 , 136 , 137 ] and ten (34.5%) were grey literature [ 27 , 55 , 63 , 71 , 74 , 102 , 123 , 127 , 128 , 138 ]. Ten reports (34.5%) discussed the effects of the asylum system on health [ 27 , 52 , 63 , 71 , 74 , 123 , 124 , 127 , 128 , 137 ] and one (3.5%) migration and health [ 50 ]. Six reports (21%) focused on culture and ethnicity [ 82 , 92 , 102 , 104 , 112 , 137 ], five reports (17%) discussed economic and environmental determinants of health [ 13 , 45 , 67 , 81 , 93 ] and five reports (17%) the health impact of social activities [ 55 , 60 , 62 , 80 , 91 ]. Of the remaining reports, one [ 65 ] discussed Brexit and mental health of European migrants and one discussed the effect of coping strategies on wellbeing in Polish migrants [ 68 ]. Most reports, 18 (62%) had a primary focus on migrant health [ 45 , 50 , 52 , 55 , 60 , 62 , 63 , 65 , 67 , 68 , 71 , 80 , 81 , 82 , 91 , 92 , 93 , 102 ], six reports (21%) discussed wider social factors in addition to health [ 74 , 123 , 124 , 127 , 128 , 138 ]. Of the remaining reports three (10%) looked at ethnic background and country of birth [ 13 , 112 , 136 ], one [ 27 ] included other vulnerable groups and one [ 137 ] included people living in China and Chinese migrants to Scotland. Thirteen reports were also categorised to one or more additional SAAP area - ten (34%) were also applicable to area 2 [ 52 , 55 , 63 , 71 , 74 , 123 , 124 , 127 , 128 , 138 ], three (10%) to area 5 [ 63 , 82 , 92 ] and one (7%) to area 4 [ 27 ].

4. Achieving public health preparedness and ensuring an effective response

Twenty-one reports were assigned to SAAP area 4 (see Fig.  4 ) [ 27 , 31 , 35 , 39 , 47 , 57 , 64 , 75 , 76 , 77 , 78 , 94 , 104 , 108 , 109 , 111 , 113 , 114 , 116 , 120 , 135 ] of which fourteen (67%) used quantitative research methods, four (19%) mixed methods and three (14%) qualitative methods. Thirteen (62%) reports were peer-reviewed journals [ 35 , 59 , 64 , 75 , 78 , 104 , 108 , 109 , 111 , 113 , 114 , 116 , 120 ] and eight (38%) grey literature [ 27 , 31 , 39 , 47 , 57 , 77 , 94 , 135 ]. Most reports (12 (57%)) focused on morbidity and mortality in migrant populations [ 31 , 35 , 64 , 75 , 76 , 78 , 104 , 108 , 109 , 113 , 114 , 116 ]. Six (29%) investigated health status and healthcare needs in migrant groups in Scotland [ 39 , 47 , 57 , 77 , 94 , 135 ]. Two reports (9.5%) analysed the epidemiology of HIV infections [ 111 , 120 ] and the remaining report focused on the health needs of young people during the covid-19 pandemic [ 27 ]. Nine reports (43%) had a primary focus on migrant health [ 39 , 47 , 55 , 64 , 75 , 76 , 77 , 78 , 94 ] while eight (38%) also analysed data by ethnicity [ 31 , 35 , 104 , 108 , 109 , 113 , 114 , 116 ]. Of the remaining reports, three (14%) included other populations within Scotland [ 27 , 111 , 120 ] and one (5%) included other characteristics in addition to health information [ 135 ]. Ten reports (48%) were also categorised to another SAAP area; one to area 2 [ 47 ], one to area 3 [ 27 ], four to area 5 [ 47 , 57 , 77 , 135 ], two to area 6 [ 111 , 120 ] and two to area 9 [ 31 , 108 ].

5. Strengthening health systems and their resilience

Twenty-nine reports were assigned to SAAP area 5 (see Fig.  4 ) [ 18 , 47 , 48 , 49 , 54 , 57 , 63 , 69 , 70 , 72 , 77 , 79 , 82 , 83 , 92 , 95 , 96 , 97 , 99 , 101 , 103 , 118 , 119 , 126 , 129 , 131 , 133 , 135 , 141 ] of which 23 (79%) used qualitative research methods. Three reports used quantitative methods (10.3%) and the remaining three used mixed methods (10.3%). Twelve reports (41%) examined migrants needs and experiences of health care [ 47 , 49 , 54 , 57 , 58 , 77 , 83 , 95 , 103 , 119 , 129 , 135 ], eight (24%) focused on pregnancy and childcare [ 63 , 70 , 92 , 96 , 97 , 99 , 101 , 118 ] and two (7%) on barriers to healthcare access [ 48 , 131 ]. Two reports (7%) evaluated healthcare programmes [ 72 , 133 ] and two focused on communication in primary care [ 79 ] and maternity services [ 69 ]. The remaining three reports (10%) covered sexual health [ 82 ], health information needs of Syrian refugees [ 126 ] and general practitioner training [ 18 ]. Nineteen (65.5%) were peer reviewed journals [ 18 , 48 , 49 , 58 , 69 , 79 , 82 , 83 , 92 , 95 , 96 , 97 , 99 , 101 , 118 , 119 , 125 , 131 , 133 ] and ten (34.5%) were grey literature [ 47 , 54 , 57 , 63 , 70 , 72 , 77 , 103 , 129 , 135 ]. Twenty-one (72%) had a primary focus on migrant health [ 18 , 47 , 48 , 49 , 54 , 57 , 58 , 63 , 69 , 70 , 72 , 77 , 79 , 82 , 83 , 92 , 95 , 96 , 97 , 99 , 101 ]. Six reports (21%) included research on other characteristics or services [ 103 , 126 , 129 , 131 , 133 , 135 ]. The remaining two reports (7%) included ethnic groups as well as migrants in the data [ 118 , 119 ]. Nineteen reports (65.5%) were also assigned to one or more other category areas: five reports (17%) to area 1 [ 47 , 70 , 72 , 103 , 129 ], five reports (17%) to area 2 [ 54 , 63 , 83 , 103 , 129 ], three reports (10%) to area 3 [ 63 , 82 , 92 ], four reports (14%) to area 4 [ 47 , 57 , 77 , 135 ], one (3.5%) to area 7 [ 119 ] and one (3.5%) to area 9 [ 48 ].

6. Preventing communicable diseases

Fourteen reports were assigned to SAAP area 6 (see Fig.  4 ) [ 56 , 61 , 87 , 88 , 89 , 90 , 105 , 106 , 107 , 111 , 115 , 117 , 120 , 122 ] of which four (31%) used quantitative methods, five (38%) used qualitative methods and five (38%) used mixed methods. Five reports (38.5%) examined immunisation behaviour [ 56 , 61 , 89 , 90 , 117 ], five (38%) on epidemiology and treatment of HIV [ 106 , 107 , 111 , 120 , 122 ]. The remaining four reports (31%) focused on tuberculosis in healthcare workers [ 115 ], malaria [ 105 ] and sexual health services [ 87 , 88 ]. Only one reports was grey literature [ 88 ], the remainder were peer-reviewed journals. Six reports (46%) had a primary focus on migrant health [ 56 , 61 , 87 , 88 , 89 , 90 ] while seven reports (54%) also included other at-risk groups in the analysis. Four reports (31%) were also assigned to another SAAP category, two (15%) to area 4 [ 111 , 120 ] and two (15%) to area 8 [ 88 , 115 ].

7. Preventing and reducing the risks posed by non-communicable diseases

Eight reports were categorised to SAAP area 7 (see Fig.  4 ) [ 46 , 51 , 59 , 84 , 85 , 86 , 98 , 119 ] of which six (75%) used qualitative research methods, one (12.5%) used quantitative methods and one (12.5%) used mixed methods. Only one report (12.5%) was grey literature [ 59 ] the remaining seven reports (87.5%) were peer-reviewed journals [ 48 , 87 , 92 , 126 , 127 , 128 , 140 ]. Three reports (37.5%) focused on health behaviours [ 51 , 85 , 98 ], two (25%) on mental health, two (25%) on diabetes and one (12.5%) on chronic disease. Seven reports(87.5%) had a primary focus on migrant health [ 46 , 51 , 59 , 84 , 85 , 86 , 98 ], with the remaining report (12.5%) including ethnic minority groups [ 119 ]. One report (12.5%) was also assigned to SAAP area number 5 [ 119 ].

8. Ensuring ethical and effective health screening and assessment

There were six reports assigned to category 8 (see Fig.  4 ) [ 53 , 88 , 100 , 110 , 115 , 121 ] of which two (33%) used a quantitative research method, three (50%) used a qualitative method and one used mixed methods. One report (14%) was grey literature [ 88 ] the remaining five reports (83%) were peer reviewed journals [ 53 , 100 , 110 , 115 , 121 ]. Three reports (50%) focused on cancer screening in migrant women [ 21 , 100 , 110 ], one (17%) analysed access to HIV testing among African migrants [ 53 ], one (17%) on T.B in healthcare workers [ 72 ] and one (17%) on sexual health [ 36 ]. Three reports (50%) had a primary focus on migrant health [ 53 , 88 , 100 ] while the remaining three reports (50%) included other at-risk groups in the analysis [ 110 , 115 , 121 ]. There were three reports which overlapped with other SAAP areas: one [ 53 ] (17%) was categorised to area 2 while two [ 88 , 115 ] (33%) were categorised to area 6.

9. Improving health information and communication

Three reports were assigned to SAAP area 9 (see Fig.  4 ) [ 31 , 108 , 130 ]. One of these (33%) used a qualitative approach, one (33%) used a quantitative approach and one (33%) used mixed methods. Two [ 108 , 130 ] (66%) were peer-reviewed journal articles and one [ 31 ] (33%) was grey literature. Two reports (66%) focused on improving migrant demographics and health information using databases [ 31 , 108 ] while one (33%) described an information-needs matrix for refugees and asylum seekers [ 130 ]. Two [ 31 , 108 ] included ethnicities in the data while one [ 130 ] had a primary focus on migrant health. Two reports [ 31 , 108 ] (66%) also applied to SAAP area 4 while one report [ 130 ] (33%) was in SAAP area 9 only.

To our knowledge this is the first scoping review conducted on migrant health in Scotland. A previous rapid literature review [ 94 ] found most research focused on health behaviours, mental health, communicable disease and use of and access to healthcare; however, the review limited migrant definition to those who had immigrated within five years and asylum seekers were not included.

In our review, the majority of reports were published from 2013 onwards, aligning with the expansion in migrant research internationally [ 142 ]. 52% used qualitative research methods, 28% used quantitative methods and 20% used mixed methods. 58% focused on migrant health: the remaining papers included other populations or health as part of a wider remit. Research funding was mostly provided by the Scottish Government, NHS, refugee charities and Universities. No studies received funding from the private sector, although this sector has the potential resource and capacity to play a key role in funding future research to improve migrant health in Scotland. Geographically, most studies took place in Glasgow (36%), nationwide (38.5%) or Edinburgh (16%) – other areas were under-represented including Aberdeen (5%), despite being the city with the largest migrant population [ 30 ]. There was a lack of studies in rural localities. These findings concur with a UK migrant health review by Burns et al. [ 23 ] where research was concentrated in larger cities and data was sparse in rural areas relative to the migrant population.

Half of the research identified that was conducted in Glasgow focused on asylum seekers/refugees. Glasgow was previously the only Scottish city to host asylum seekers [ 143 ] and currently supports the most asylum seekers of any local authority in the UK [ 29 ]. In April 2022, the UK government widened the Asylum dispersal scheme to all local authorities [ 144 ]. Around 70% of Scotland’s refugee support services are based in Glasgow and the South-west [ 145 ]. As reduced access to services may impact the health of asylum seekers, research in Glasgow may not be generalizable to other regions of Scotland.

Almost one-third (30%) of all reports focused on asylum seekers and refugees – an overrepresentation given that only 18% of migrants to the UK are asylum seekers [ 146 ] and as low as 2% of all migrants in Scotland [ 147 ]. Asylum seekers and refugees are at risk of poor health due to trauma, difficult journeys, overcrowded camps, poor nutrition and lack of access to healthcare [ 148 ]. They have worse maternity outcomes and increased rates of mental illness [ 149 ]. Increased research on health of asylum seekers and refugees is necessary due to their additional vulnerabilities [ 142 ]. However, asylum seeker’s country of origin was generally not specified. Asylum seekers have heterogenic backgrounds [ 150 ] and nationality and trauma experience affect health status [ 151 ]. Further research focused on specific nationalities of asylum seekers would enhance understanding of the health needs in this population.

Almost one-third (31%) of studies did not specify a migrant group. This concurs with a Norwegian migrant health study by Laue et al. [ 152 ] where 36% of research did not identify country of birth. Where nationality was identified, Polish, African and South Asian were most prevalent. Poles are the largest migrant group in Scotland, however for the other most common immigrant groups of Irish, Italian and Nigerian [ 30 ] there was an absence of research. No studies took place on Nigerian migrants – nine studies indicated African populations, but country of birth was not specified. Since March 2022, 23,000 Ukrainians have migrated to Scotland [ 153 ], however no studies on Ukrainians were identified currently. Research may be underway which is yet to be published.

Only one study explored the impact of Brexit on European migrants’ health despite 56% of migrants to Scotland being EU nationals [ 30 ]. Again, research may be taking place currently, which is yet to be published. No studies involved undocumented migrants despite this populations’ high rates of poor physical/mental health exacerbated by poor housing and working conditions [ 154 ]. An estimated 7.2–9.5% of the workforce in the UK are migrant workers who have higher risks of poor working conditions and injury [ 155 ]. Scotland depends on a migrant workforce for some industries such as agriculture [ 156 ] but only two research papers specified migrant workers.

Most research papers related to the right to health of refugees (SAAP 2), social determinants of health (SAAP 3), public health planning (SAAP 4) and strengthening health systems (SAAP 5). Areas with less research were frameworks for collaborative action (SAAP 1), preventing communicable disease (SAAP 6), preventing non-communicable disease (SAAP 7) and health screening and assessment (SAAP 8). Only three studies related to improving health information and communication (SAAP 9). Lebano et al. [ 12 ] conducted a literature review of migrant health in Europe and found data collection unreliable and disorganised. There is a lack of data on the numbers and types of migrants entering Scotland and research tends not to differentiate between ethnic minorities and migrants [ 94 ]. As poor-quality information hinders surveillance and planning of services SAAP area 9 is an important consideration for increased research.

Villarroel et al. [ 24 ] also found more research in SAAP areas 3 to 5 and less in areas 6 to 9. However, their study returned no results in category 1, collaborative action, or 2, the right to health of refugees, while this study assigned 9% of articles to category 1 and 19% to category 2. Most articles in our study relating to categories 1 and 2 were grey literature, which was excluded from the original Irish scoping review. This highlights a potential difference in the focus of peer-reviewed articles compared to government/refugee charity commissioned reports. Collaborative action and the right to health of refugees and asylum seekers are entwined in Scotland due to the complex policy environment; the social determinants of health such as housing, education, welfare rights and social integration are influenced by a variety of UK and Scottish statutory bodies as well as third sector organisations [ 157 ]. Despite this complexity, organisations work well together [ 158 ]. Further academic research in this area would enhance joint working practices and networks.

A scoping review in the UK [ 23 ] found similar quantities of research corresponding to SAAP areas 3, 2 and 9. However in Scotland areas 1, 5 and 8 were a combined 44% of included papers compared with 27.8% of results on health systems and structures in Burns et al’s [ 23 ] study. Almost half of the articles in SAAP areas 1,5 and 8 were grey literature, which was not included in Burns et al’s [ 23 ] review. Conversely, Burns et al. [ 23 ] found 81.9% of research in the UK related to epidemiology, equivalent to SAAP categories 4,6 and 7. In a Norwegian scoping review of migrant health [ 152 ] 65% of research was related to epidemiological data on health and disease. Only 42% of the research in this current study related to epidemiological data; the quantity of evidence was reduced by excluding combined research from the UK. As Scotland has higher mortality and morbidity than elsewhere in the UK [ 29 ] it is important to undertake further epidemiological research limited to Scotland.

Strengths and weaknesses

Strengths of this review include the use of the WHO’s SAAP categories [ 7 ] to classify data, in accordance with the Villarroel et al’s [ 24 ] study: this means results are linked to policy on migrant health and facilitates comparability to the Irish study results. Additionally results include data on migrant groups, locality, and funding of included papers; these highlight potential omissions for future research consideration. Results include diverse research methods and published and grey literature giving a wide overview of available evidence, reported using the Preferred Reporting Items for Systematic reviews and Meta-Analyses for Scoping Reviews (PRISMA-ScR) checklist (see Additional File 3 ) [ 159 ].

Limitations included the lack of an open-access protocol and search limitations of English language and selected databases. This means some relevant reports may be omitted. Due to time and resource limitations no quality appraisal was planned for included reports. Whilst we did not synthesise the findings for each topic area and migrant group, future systematic reviews could be undertaken to address this limitation and build on this work.

Conclusions

Immigration and ethnic diversity in Scotland have increased since 2002 which is reflected in the expansion of migrant health research. This review highlights evidence gaps including a lack of research in rural areas, undocumented migrants and migrant workers. There is a tendency to cluster asylum seekers together rather than differentiate between national groups. Within the SAAP areas there is less evidence relating to collaborative action, preventing communicable disease, preventing non-communicable disease and health screening and assessment. Further research is required on improving health information and communication for migrant populations in Scotland – a significant omission given the importance of accurate information for health service planning.

Availability of data and materials

All data analysed during this review comes from the papers listed in Additional file 2 .

Abbreviations

European Union

Human Immunodeficiency Virus

National Health Service

Strategy and Action Plan

The Scottish Health and Ethnicity Linkage Study

United Kingdom

World Health Organisation

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Acknowledgements

Thank-you to Professor Anne MacFarlane and PHD student Anne Cronin, of the University of Limerick, Ireland for sharing the coding guidelines currently used in an update to Villarroel et. al’s 2019 study on Migrant Health in the Republic of Ireland.

No funding was received for this work, which was undertaken as G. Petrie’s Master of Public Health dissertation module at the University of Stirling.

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Petrie, G., Angus, K. & O’Donnell, R. A scoping review of academic and grey literature on migrant health research conducted in Scotland. BMC Public Health 24 , 1156 (2024). https://doi.org/10.1186/s12889-024-18628-1

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SYSTEMATIC REVIEW article

The histological and molecular characteristics of early-onset colorectal cancer: a systematic review and meta-analysis.

• 1 School of Medicine and Public Health, Carbone Cancer Center, University of Wisconsin-Madison, Madison, WI, United States
• 2 School of Medicine and Public Health, Department of Population Health Sciences, University of Wisconsin-Madison, Madison, WI, United States

Background: Early-onset colorectal cancer (CRC), defined as diagnosis before age 50, has increased in recent decades. Although more often diagnosed at advanced stage, associations with other histological and molecular markers that impact prognosis and treatment remain to be clarified. We conducted a systematic review and meta-analysis concerning the prevalence of prognostic and predictive tumor markers for early- vs. late-onset CRC, including oncogene mutations, microsatellite instability (MSI), and emerging markers including immune cells and the consensus molecular subtypes.

Methods: We systematically searched PubMed for original research articles published between April 2013–January 2024. Included studies compared the prevalence of tumor markers in early- vs. late-onset CRC. A meta-analysis was completed and summary odds ratios (ORs) with 95% confidence intervals (CIs) were obtained from a random effects model via inverse variance weighting. A sensitivity analysis was completed to restrict the meta-analysis to studies that excluded individuals with Lynch syndrome, a hereditary condition that influences the distribution of tumor markers for early-onset CRC.

Results: In total, 149 articles were identified. Tumors from early-onset CRC are less likely to include mutations in KRAS (OR, 95% CI: 0.91, 0.85-0.98), BRAF (0.63, 0.51-0.78), APC (0.70, 0.58-0.84), and NRAS (0.88, 0.78-1.00) but more likely to include mutations in PTEN (1.68, 1.04-2.73) and TP53 (1.34, 1.24-1.45). After limiting to studies that excluded Lynch syndrome, the associations between early-onset CRC and BRAF (0.77, 0.64-0.92) and APC mutation (0.81, 0.67-0.97) were attenuated, while an inverse association with PIK3CA mutation was also observed (0.88, 0.78-0.99). Early-onset tumors are less likely to develop along the CpG Island Methylator Phenotype pathway (0.24, 0.10-0.57), but more likely to possess adverse histological features including high tumor grade (1.20, 1.15-1.25), and mucinous (1.22, 1.16-1.27) or signet ring histology (2.32, 2.08-2.57). A positive association with MSI status (1.31, 1.11-1.56) was also identified. Associations with immune markers and the consensus molecular subtypes are inconsistent.

Discussion: A lower prevalence of mutations in KRAS and BRAF is consistent with extended survival and superior response to targeted therapies for metastatic disease. Conversely, early-onset CRC is associated with aggressive histological subtypes and TP53 and PTEN mutations, which may serve as therapeutic targets.

1 Introduction

Colorectal cancer (CRC) is the second leading cause of cancer mortality in the United States ( 1 ). The incidence of CRC has steadily declined since the 1980s, largely attributed to greater uptake of colonoscopy screening by adults aged 50 years and older ( 2 ). Concurrently, the incidence of sporadic early-onset CRC, generally defined as CRC diagnosis before age 50 without an underlying hereditary cause, has significantly increased since the mid-1990s ( 2 ). Data from the Surveillance, Epidemiology, and End Results (SEER) program reflect a 2-3% annual increase in the incidence of early-onset CRC ( 3 ). The elevated incidence of early-onset CRC may be explained by birth cohort effects where more recent birth cohorts have increased prevalence of obesity and type 2 diabetes, lower levels of physical activity, and more often consume western-style diets characterized by lower consumption of fruits and vegetables ( 4 ), as well as changes in the composition of the gut microbiome ( 2 ). While early-onset CRC may be caused by hereditary conditions defined by germline mutations in DNA mismatch-repair genes (i.e. Lynch syndrome) or in the tumor suppressor APC (i.e. familial adenomatous polyposis) ( 5 ), these inherited conditions account for a relatively small percentage of early-onset CRC and do not explain the increased prevalence observed in recent decades ( 2 ).

CRC is a heterogeneous disease and the clinicopathological and molecular characteristics of tumors may influence prognosis and response to treatment ( 6 ). Beyond tumor stage, multiple potential prognostic and predictive markers have been identified, including mutations in oncogenes such as KRAS , BRAF , PIK3CA , and TP53 , histological subtypes including mucinous and signet ring carcinomas, and the microsatellite instability (MSI) phenotype ( 7 ). Further, several novel prognostic markers have recently been identified, including immune markers in the tumor microenvironment ( 8 ) and the CRC consensus molecular subtypes ( 9 ). It is anticipated that the continued characterization of molecular phenotypes in CRC will augment traditional clinical markers for therapeutic decision making and support the development of targeted approaches to treatment ( 10 ).

Given the increasing rate of early-onset CRC, recent publications have highlighted potential differences in the clinicopathological and molecular characteristics of tumors based on age of onset ( 11 – 14 ). However, it is currently unclear whether early-onset CRC is distinct from late-onset disease in terms of molecular characteristics and tumor developmental pathways ( 15 ). Understanding the molecular characteristics of early-onset CRC is necessary to guide the development of therapeutic approaches for this condition and to address underlying causes. Therefore, we have completed a systematic review and meta-analysis to comprehensively summarize the evidence linking early-onset CRC to differences in prognostic and predictive tumor markers, including oncogene mutations, histological subtypes, MSI status, as well as anti-tumor immunity and the consensus molecular subtypes.

2.1 Literature review

Articles for this systematic review were identified utilizing a Pubmed search incorporating PRISMA guidelines ( 16 ). Given the wide breadth of the topic and the limited number of relevant articles published prior to 2013, the search was limited to peer-reviewed, original research articles published in English from the last 10 years (April 2013 – April 2023), with relevant keywords and medical subject headings included in the title and/or abstract. The literature review was repeated in January 2024 to identify recently published articles. Specific biomarker terms to include in the literature search were identified from prior reviews, and the search terms “biomark*”, “mark*”, and “character*” were included to capture potentially novel prognostic markers. All search terms included for the literature review are displayed in Supplementary Table S1 . Manuscripts were included that reported the prevalence of prognostic biomarkers in CRC tumors separately for early- vs. late-onset disease. Articles were excluded if the prevalence of tumor clinicopathological or molecular biomarkers were not provided for participants with CRC (see Figure 1 flowchart), or if there was no comparison between early- vs. late-onset CRC (or if the comparison was limited to tumor stage or location only). Articles were also excluded that described hereditary CRC only (e.g. Lynch syndrome), site-specific metastases, or included non-CRC cancers in the analysis samples. For the purposes of this analysis, early-onset disease was defined as CRC diagnosed prior to age 50. To avoid misclassification of early- and late-onset CRC, we excluded papers where late-onset CRC was defined as ≥ 40 years at diagnosis or younger, or where early-onset CRC was defined as ≤ 60 years at diagnosis or older. Lastly, to limit sample overlap where possible, we excluded studies if there was evidence of complete overlap in sample and markers reported with a previously published study, or if a study reported the same outcome in a subsample of a previous study.

Figure 1 Literature review flowchart. a Inappropriate study design includes studies concerning colorectal cancer incidence, colonoscopy or other colorectal cancer screening, population level summary statistics for colorectal cancer, and studies of colorectal cancer in model organisms or in vitro studies. b Markers of interest include oncogene mutations in KRAS , NRAS , BRAF , PIK3CA , PTEN , TP53 , APC , and HER2 ; histological phenotypes including high-grade tumors and mucinous or signet ring histology; molecular carcinogenesis pathways including microsatellite instability and the CpG island methylator phenotype (CIMP); and novel tumor prognostic phenotypes including immune markers in the tumor microenvironment and the consensus molecular subtypes. c Studies where late-onset colorectal cancer was defined as ≥ 40 years at diagnosis (or younger), or early-onset CRC was defined as ≤ 60 years at diagnosis (or older).

The systematic review and meta-analysis was limited to the following markers that have been shown associations with CRC survival and/or therapeutic response in CRC: oncogene mutations in KRAS ( 17 – 20 ), NRAS ( 17 , 21 , 22 ), BRAF ( 17 , 19 , 23 , 24 ), PIK3CA ( 17 , 25 , 26 ), PTEN ( 27 , 28 ), TP53 ( 29 ), APC ( 30 , 31 ), and HER2 amplifications ( 32 – 34 ); histological phenotypes including high-grade tumors ( 35 , 36 ) and mucinous ( 37 , 38 ) or signet ring histology ( 38 , 39 ); molecular carcinogenesis pathways including MSI ( 40 ) and the CpG island methylator phenotype (CIMP) ( 41 ); and novel tumor prognostic phenotypes including immune markers ( 42 , 43 ) in the tumor microenvironment and the consensus molecular subtypes ( 9 , 44 ). Because it is well-established that early-onset CRC is associated with advanced tumor summary stage at diagnosis and rectal tumor location, these markers are not summarized in this review. The literature review was completed by two authors (T.L. and L.P) independently. Disagreements between reviewers were resolved by further review of the manuscript to determine whether the study included a comparison of tumor markers of interest between early- and late-onset CRC. The final decision to include a manuscript was made by the lead author. In total, 1,694 articles were identified from the literature search and 149 were eligible for review ( Figure 1 ). For each study, the potential for bias was evaluated by the lead author using the Newcastle-Ottawa Scale adapted for cross-sectional studies ( 45 ). Pre-registration of the systematic review protocol was not performed.

2.2 Meta-analysis

From each eligible study, the number of mutant and wild-type tumors for each marker in early- and late-onset CRC was extracted by the lead author. Data extraction was completed in duplicate, and the results from the two extractions were compared to identify any errors or inconsistencies in the sample sizes, which were subsequently revised after further review of the original article. If these data were not available from the manuscript, sample sizes were requested from the corresponding author. One study was excluded for which we were unable to obtain the necessary sample sizes from each group ( 46 ). When necessary, sample sizes for separate age groups were combined to create a single category for early-onset and late-onset CRC. For most studies, age 45 or 50 at diagnosis was utilized as the threshold to distinguish early- vs. late-onset CRC, although occasionally other classifications were employed (see Supplementary S2 ). For each study, sample characteristics including overall sample size, country, tumor stage, sex, or other distinguishing features were also extracted. For each marker, an odds ratio (OR) and 95% confidence interval (CI) were calculated using a standard equation ( 47 ). For mutations in oncogenes KRAS, NRAS, BRAF, PIK3CA, PTEN, TP53 , and APC , as well as MSI status and histological subtypes, meta-analyses were completed to compare the prevalence in tumors from early- vs. late-onset CRC. Due to the wide variety of immune markers that have been reported, a meta-analysis was not attempted for the comparison of immune phenotypes in the tumor microenvironment. For each marker that was meta-analyzed, a pooled OR with 95% CI was obtained from a random effects model via inverse variance weighting. The random effects model was selected a priori , as between-study heterogeneity is plausible given variability in the definition of early-onset CRC, as well as differences in tumor location, race, nationality and stage between studies. The random effects meta-analysis is capable of providing unbiased estimates in the presence of heterogeneity and will generally provide more conservative estimates than the fixed-effects model (which assumes no between-study heterogeneity) ( 48 ). Heterogeneity was determined via the Cochrane’s Q statistic and the I 2 statistic. Significant heterogeneity was defined as P <.05 for Cochrane’s Q or I 2 ≥ 50%. To determine whether the meta-analysis estimates were influenced by a single study, a ‘leave-one-out’ sensitivity analysis was conducted for each marker. Because Lynch syndrome may influence the prevalence of tumor markers for individuals with early-onset CRC, a second sensitivity analysis was completed to limit the analysis to studies that specifically excluded individuals with Lynch syndrome or family history of CRC, or that restricted the sample to microsatellite stable tumors. All statistical tests were two-sided, with statistical significance defined using a threshold of P <.05. All meta-analyses were completed using Review Manager 5.4.1 from Cochrane.

In total, 149 articles were reviewed that compared the prevalence of clinicopathological tumor markers in early- vs. late-onset CRC. All meta-analysis results are summarized in Table 1 . Sample characteristics and references for all included studies are presented in Supplementary Table S2 . Results of the bias assessment utilizing the Newcastle-Ottawa Scale are presented in Supplementary Table S4 .

Table 1 Summary of meta-analysis results showing associations between early-onset colorectal cancer and the prevalence of tumor markers, compared to late-onset colorectal cancer.

3.1 Oncogene mutations

The number of studies identified for the following markers is as follows: KRAS mutation ( 49 ); BRAF mutation ( 49 ); NRAS mutation ( 20 ); PIK3CA mutation ( 21 ); PTEN mutation ( 8 ); HER2 amplifications ( 5 ); APC mutation ( 19 ); TP53 mutation ( 20 ). For early-onset CRC, there is evidence for a significantly lower prevalence of mutations in KRAS ( Figure 2 , OR 0.91, 95% CI 0.85-0.98), BRAF ( Figure 3 , OR 0.63, 95% CI 0.51-0.78) and APC ( Figure 4 , OR 0.70, 95% CI 0.58-0.84) compared to late-onset CRC. Early-onset CRC was associated with non-significantly lower prevalence of mutations in NRAS ( Figure 5 , OR 0.88, 95% CI 0.78-1.00, p = .06). Conversely, early-onset CRC is associated with a higher prevalence of mutations in TP53 ( Figure 6 , OR 1.34, 95% CI 1.24-1.45) and PTEN ( Figure 7 , OR 1.68, 95% CI 1.04-2.73). There was no significant difference in the prevalence of PIK3CA mutations ( Supplementary Figure S1 , OR 0.95, 95% CI 0.86-1.05), or HER2 amplifications ( Supplementary Figure S2 , OR 1.64, 95% CI 0.86-3.14). Significant inter-study heterogeneity was observed for mutations in KRAS , BRAF , PTEN , and APC . Hazard ratios for oncogene mutations were stable in the leave-one-out sensitivity analysis ( Supplementary Table S3 ), although the association for NRAS and PTEN mutations did not always reach statistical significance.

Figure 2 Odds ratios for KRAS mutation in early-onset CRC. Data presented as odds ratios (95% confidence interval) for KRAS mutation in early-onset relative to late-onset colorectal cancer. The pooled odds ratio is obtained via a random effects model using inverse variance weighting. AACR, American Association for Cancer Research; MDACC, MD Anderson Cancer Center; MSI, microsatellite instability; MSS, microsatellite stable.

Figure 3 Odds ratios for BRAF mutation in early-onset CRC. Data presented as odds ratios (95% confidence interval) for BRAF mutation in early-onset relative to late-onset colorectal cancer. The pooled odds ratio is obtained via a random effects model using inverse variance weighting. AACR, American Association for Cancer Research; MDACC, MD Anderson Cancer Center; MSI, microsatellite instability; MSS, microsatellite stable.

Figure 4 Odds ratios for APC mutation in early-onset colorectal cancer. Data presented as odds ratios (95% confidence interval) for APC mutation in early-onset relative to late-onset colorectal cancer. The pooled odds ratio is obtained via a random effects model using inverse variance weighting. AACR, American Association for Cancer Research; COH, City of Hope National Medical Center; CI, confidence interval; EO-CRC, early-onset colorectal cancer; MDACC, MD Anderson Cancer Center; MSKCC, Memorial Sloan Kettering Cancer Center; UCD, University of California, Davis.

Figure 5 Odds ratios for NRAS mutation in early-onset colorectal cancer. Data presented as odds ratios (95% confidence interval) for NRAS mutation in early-onset relative to late-onset colorectal cancer. The pooled odds ratio is obtained via a random effects model using inverse variance weighting. AACR, American Association for Cancer Research; CI, confidence interval; EO-CRC, early-onset colorectal cancer; MDACC, MD Anderson Cancer Center.

Figure 6 Odds ratios for TP53 mutation in early-onset colorectal cancer. Data presented as odds ratios (95% confidence interval) for TP53 mutation in early-onset relative to late-onset colorectal cancer. The pooled odds ratio is obtained via a random effects model using inverse variance weighting. AACR, American Association for Cancer Research; CI, confidence interval; EO-CRC, early-onset colorectal cancer; MDACC, MD Anderson Cancer Center; MSI, microsatellite instability; MSS, microsatellite stability.

Figure 7 Odds ratios for PTEN mutation in early-onset colorectal cancer. Data presented as odds ratios (95% confidence interval) for PTEN mutation in early-onset relative to late-onset colorectal cancer. The pooled odds ratio is obtained via a random effects model using inverse variance weighting. AACR, American Association for Cancer Research; CI, confidence interval; EO-CRC, early-onset colorectal cancer; MDACC, MD Anderson Cancer Center.

Fifty studies were identified that specifically excluded individuals with Lynch syndrome or family history of CRC, or that restricted the analysis to individuals with microsatellite stable tumors ( Table 1 ; Supplementary Table S2 ). Compared to the full analysis, the association between early-onset CRC and BRAF (OR 0.77, 95% CI 0.64-0.92) and APC mutations (OR 0.81, 95% CI 0.67-0.97) were attenuated but remained statistically significant, while the associations with KRAS , NRAS , and TP53 mutations were similar. Further, an inverse association between early-onset CRC and PIK3CA mutation was also observed (OR 0.88, 95% CI 0.78-0.99).

3.2 Molecular carcinogenesis pathways

There were 10 studies that compared the prevalence of CIMP-high status in early- vs. late-onset CRC, and 64 studies that compared MSI status. Individuals with early-onset CRC had significantly lower odds for CIMP-high tumors compared to individuals with late-onset disease ( Supplementary Figure S3 , OR 0.24, 0.10-0.57), but significantly higher odds for the MSI phenotype ( Supplementary Figure S4 , OR 1.31, 1.11-1.56). Significant heterogeneity was observed for both markers. Associations were stable in the leave-one-out sensitivity analysis ( Supplementary Table S3 ), and after limiting the analysis to studies that excluded individuals with Lynch syndrome or family history of CRC ( Table 1 ).

3.3 Histological characteristics

There were 86 studies that compared the prevalence of high-grade tumors (i.e. poorly differentiated or undifferentiated tumors) in early- vs. late-onset CRC, 57 studies that compared the prevalence of mucinous histology (or mucinous characteristics), and 44 studies that reported on signet ring cell carcinomas. In early-onset CRC, there was evidence for a significantly higher prevalence of high-grade (i.e., poorly differentiated) tumors ( Supplementary Figure S5 , OR 1.20, 95% CI 1.15-1.25), as well as mucinous tumors ( Supplementary Figure S6 , OR 1.22, 95% CI 1.16-1.27), and signet ring cell carcinomas ( Supplementary Figure S7 , OR 2.32, 2.08-2.57). Significant inter-study heterogeneity was observed for all histological markers. All associations were stable in the leave-one-out sensitivity analysis ( Supplementary Table S3 ) and after limiting the analysis to studies that excluded individuals with Lynch syndrome or family history of CRC ( Table 1 ).

3.4 Immune markers

There have been nine studies to investigate age differences in the immune cell populations of CRC tumors, with inconsistent results ( 49 – 57 ). Du et al. reported that Chinese patients with sporadic early-onset CRC showed significantly higher densities of multiple immune cell populations in the tumor microenvironment compared to patients with late-onset disease, including higher levels of B cells, CD4+ T cells, CD8+ T cells, neutrophils, macrophages, and dendritic cells ( 50 ). By contrast, Ugai et al. reported no significant differences in the populations of T cells, macrophages, and other myeloid cells in participants with early- vs. late-onset CRC from the Nurses’ Health Study and Health Professionals Follow-up Study ( 51 ). In a small study of 14 tumors utilizing single cell RNA sequencing, Li et al. reported that early-onset CRC was associated with lower levels of effector CD8+ T cells and antigen-presentation in the tumor microenvironment, but higher levels of naïve CD8+ T cells and immunosuppressive regulatory T cells compared to individuals with late-onset disease, suggesting an impaired anti-tumor immune response for early-onset CRC ( 54 ). Because MSI status may influence the anti-tumor immune response, recent studies have examined associations between early-onset CRC and tumor lymphocyte populations in samples limited to microsatellite stable tumors, or after careful exclusion of participants with Lynch syndrome ( 56 , 57 ). In a matched analysis of microsatellite stable tumors, Lu et al. (2023) reported that there was no significant differences between early- and late-onset CRC for the infiltration of 22 different lymphocyte populations in the tumor microenvironment ( 57 ). Likewise, Andric et al. found no significant difference for five lymphocyte populations (total T cells, conventional CD4+ and CD8+ T cells, regulatory T cells, and γδ T cells) in a matched sample limited to cases of sporadic CRC ( 56 ). Other studies have reported no significant differences between early and late-onset CRC for the density of total tumor infiltrating lymphocytes ( 53 , 55 ).

3.5 The consensus molecular subtypes

There have been six studies to determine the distribution of consensus molecular subtypes (CMS) for CRC by age at diagnosis ( 50 , 57 – 61 ). Utilizing tumor tissues samples from 626 individuals diagnosed with CRC from The Cancer Genome Atlas and MD Anderson Cancer Center, Willauer reported that the CMS1 subtype was more common among patients aged 30-39 years at diagnosis (46%) compared to older participants, while the CMS4 subtype was less common (13%) ( 58 ). Conversely, in a smaller study from the Nanjing Colorectal Cancer Cohort, Du et al. reported a higher prevalence of the CMS4 subtype in early- vs. late-onset CRC (36.7% vs. 12.2%, respectively), although the comparison between age groups did not reach statistical significance ( 50 ). Recent results, including from a small sample of South Korean participants ( 59 ) and additional analyses of The Cancer Genome Atlas ( 60 , 61 ) did not show any significant association between early-onset tumors and the distribution of consensus molecular subtypes.

4 Discussion

Sporadic early-onset CRC is a significant public health concern, increasing by 2-3% per year in the U.S. since 1990 ( 3 , 62 ). Early-onset CRC is more often diagnosed at advanced stages compared to late-onset disease ( 63 , 64 ). However, there is inconsistent evidence that survival varies between early- and late-onset CRC ( 65 , 66 ), complicated by reports that younger patients receive more aggressive systemic treatment ( 67 – 69 ). Thus, international guidelines do not endorse separate treatment recommendations for early-onset disease ( 70 ). Investigating the associations between early-onset tumors and molecular and histological characteristics, and novel tumor markers including immune cell populations, may help to guide the development of therapies that benefit early-onset CRC. Further, highlighting associations between early-onset CRC and tumor markers may aid in the design of clinical trials for targeted therapies. To the authors’ knowledge, this is the first comprehensive systematic review and meta-analysis of tumor prognostic and predictive markers in early-onset CRC. We found that early-onset CRC was associated with a lower prevalence of oncogene mutations in KRAS , BRAF , NRAS , and APC , but a higher prevalence of TP53 and PTEN mutations and adverse histologic subtypes, with inconsistent associations for immune cell populations and the consensus molecular subtypes.

KRAS , BRAF , and NRAS encode proteins that act downstream of the epidermal growth factor receptor (EGFR) and activate Mek/Erk signaling ( 21 , 71 ). Mutations in these oncogenes are negative predictive markers for EGFR inhibition in metastatic CRC ( 17 , 18 ) and are associated with inferior survival outcomes across tumor stage ( 19 , 20 , 23 , 72 ), including for early-onset CRC ( 73 – 75 ). Early-onset CRC is associated with a lower prevalence of mutations in these genes compared to late-onset disease, indicating that individuals with metastatic early-onset CRC may be more likely to benefit from EGFR inhibition. Notably, the association with NRAS mutations was not statistically significant, which may be due to the scarcity of this marker ( 76 ). Further, the association with BRAF mutation was attenuated but still statistically significant in studies that excluded individuals with Lynch syndrome, who are less likely to have BRAF mutations compared to sporadic disease ( 77 ). Further, this sensitivity analysis revealed an inverse association with PIK3CA mutation, which has also been linked to higher risk for mortality and resistance to EGFR inhibition ( 17 , 78 ). Conversely, early-onset CRC was associated with a higher proportion of mutations in tumor suppressor PTEN , which encodes a lipid-phosphatase that suppresses the activity of PI3k/Akt/mTOR signaling and interacts with the EGFR pathway ( 27 ). Loss of PTEN activity has been linked to resistance to EGFR inhibition in metastatic CRC ( 79 ) but is not currently used in clinical decision making. Pharmaceutical therapies to restore normal PTEN activity are under development but have not been evaluated in CRC. Early-onset CRC was associated with a significantly higher prevalence of TP53 mutations, which cause loss of p53 tumor suppressor activity and pro-tumorigenic gain of function effects that accelerate cell proliferation, angiogenesis, and metastasis ( 80 ). TP53 mutations are found in approximately 60% of tumors and may promote resistance to EGFR inhibitors and chemotherapies that rely on wild type p53 to induce cellular apoptosis (e.g. 5-fluorouracil and Oxaliplatin) ( 29 ). Consequently, targeted therapies to restore wild type p53 activity or degrade mutant p53, or to inhibit downstream effector pathways, are currently being investigated in clinical trials ( 81 ). Potentially, individuals with early-onset CRC may be more likely to benefit from treatments that inhibit pro-tumorigenic p53 activity and should be targeted for enrollment in these trials.

Early-onset CRC was associated with a lower prevalence of APC mutation, a key driver of the canonical adenoma-carcinoma pathway ( 82 ). APC mutations are present in approximately 80% of CRC tumors ( 11 , 12 , 14 ), and recent evidence indicates that APC -mutant tumors are associated with extended overall and progression-free survival compared to wild type ( 30 , 31 ) ( 5 ). Notably, the association with APC mutation was attenuated but still statistically significant when limiting the analysis to studies that excluded individuals with Lynch syndrome, or that included microsatellite stable tumors only. Individuals with early-onset CRC had a higher prevalence of MSI, defined by a high density of somatic mutations in short, non-coding sequences caused by defects in DNA mismatch repair ( 40 ). MSI is associated with lower risk for overall mortality and distant metastases compared to microsatellite stable tumors, including in early-onset CRC ( 75 ). Further, MSI tumors secrete truncated proteins that trigger an anti-tumor immune response ( 83 ), and consequently MSI is a positive predictor for response to immune checkpoint inhibitors ( 83 ). Our findings therefore highlight the importance of MSI testing for individuals younger than 50, in accordance with clinical guidelines ( 70 ). Unexpectedly, the association between early-onset CRC and MSI status was modestly strengthened in studies that excluded individuals with known Lynch syndrome, which causes tumors with MSI ( 84 ). Because a significant proportion of individuals with Lynch syndrome may be unaware of the condition ( 85 ), it is possible that the exclusion of Lynch syndrome was incomplete in some studies. Early-onset CRC was associated with a lower prevalence of the CpG island methylator phenotype (CIMP), characterized by methylation and inactivation of tumor-suppressor genes ( 86 ). Although CIMP has been linked to poor prognosis in multiple studies, it currently has limited value as a prognostic marker due to a lack of standardized assessment and competing effects of MSI and BRAF mutation, which are associated with CIMP ( 41 ).

We also found that early-onset CRC is associated with higher odds for tumors with more aggressive histological features, including poorly differentiated tumors, mucinous carcinomas, and signet ring cell carcinomas ( 38 , 87 ). The association with signet ring features was especially pronounced (OR [95% CI]: 2.32 [2.08-2.57]). Although signet ring carcinomas comprise only 1% of CRC tumors ( 39 ), this feature is present in 2-3% of early-onset tumors. A recent meta-analysis showed that signet ring carcinomas were associated with significantly higher risk for overall mortality and recurrence compared to conventional adenocarcinomas ( 88 ). Results were similar for mucinous tumors, which comprise approximately 10-15% of CRCs ( 89 ). The associations between histological subtypes and colorectal cancer mortality, especially poorly differentiated tumors and signet ring carcinomas, have been validated in early-onset CRC ( 90 – 93 ). Currently, there are no treatments that specifically target mucinous or signet ring cell carcinomas and treatment guidelines do not distinguish between histological subtypes ( 70 ).

The observed associations between early-onset CRC and certain histological and molecular tumor characteristics may be explained in part by differences in tumor location ( 94 ). Approximately 30% of early-onset tumors are located in the rectum, versus 20% of late-onset tumors ( 64 , 95 ). KRAS, BRAF, PIK3CA , and NRAS mutations are enriched in proximal tumors ( 96 , 97 ) while TP53 mutations are enriched in rectal tumors ( 98 ). Notably, studies that were limited to individuals with tumors in the distal colon or rectum have not shown a consistent association between early-onset CRC and the presence of oncogene mutations ( 46 , 55 , 56 , 99 – 102 ). For example, a study with more than 1,000 distal and rectal tumors showed no significant age difference in KRA S, BRAF, NRAS , PIK3CA , TP53 , or APC mutations ( 46 ). Conversely, in a large-scale analysis with detailed stratification by tumor location, Ugai et al. found that early-onset CRC had a lower prevalence of BRAF mutations for all tumor sites except the sigmoid colon and rectum ( 103 ). Notably, aggressive histological subtypes are overrepresented in the proximal colon ( 104 ), and consequently the association with early-onset CRC is not explained by differences in tumor location.

We found inconsistent evidence linking early-onset CRC to differences in ‘novel’ tumor prognostic and predictive markers including populations of immune cells in the tumor microenvironment ( 8 ). A recent meta-analysis demonstrated that a higher density of tumor infiltrating lymphocytes was associated with reduced overall mortality among 20,015 individuals with CRC (HR [95% CI]: 0.65 [0.54-0.77]) ( 42 ), while others have shown that an ‘immunoscore’ encompassing cytotoxic T cells and CD3+ cells was a superior prognostic marker compared to the tumor stage ( 105 , 106 ). Currently, the association between early-onset CRC and the anti-tumor immune response has been inconsistent ( 48 – 50 , 52 , 53 , 55 , 56 , 58 ). Notably, higher rates of MSI in early-onset CRC due to Lynch syndrome may obscure associations with immune markers in sporadic disease, as MSI tumors trigger a robust anti-tumor immune response ( 83 ). Studies limited to microsatellite stable tumors or that carefully excluded participants with hereditary syndromes have tended to show no significant differences in immune cell populations between early- and late-onset CRC ( 51 , 56 , 57 ). Likewise, there is currently no consistent evidence that the distribution of consensus molecular subtypes differs between early- and late-onset CRC, with most studies reporting null findings ( 50 , 57 , 59 – 61 ). The consensus molecular subtypes have shown to be a robust predictor of mortality outcomes independent of tumor stage ( 107 ), but to the authors’ knowledge have not been validated specifically in early-onset CRC. Further, the identification of novel molecular subtypes in early-onset CRC based on tumor gene expression is an area for future research.

Strengths of this study include the comprehensive nature of the search strategy, as we were able to summarize the evidence for age-related differences in the prevalence of established tumor prognostic markers as well as emerging markers including immune cell populations in the tumor microenvironment and the consensus molecular subtypes. Further, the large number of studies identified for most markers allowed for relatively precise estimates of the association with early-onset CRC. Lastly, to better understand the associations between early-onset CRC and tumor markers in sporadic disease, we completed a sensitivity analysis limited to studies that excluded individuals with known Lynch syndrome (or family history of CRC). This analysis is also attended by several limitations. Due to the breadth of the review, our literature search was limited to original research studies published within the last ten years in Pubmed. Consequently, it is possible that a relevant study was missed. However, this is unlikely to be a significant limitation given the paucity of large tumor genomic studies published prior to 2013 and the comprehensive nature of our search strategy. Further, there was evidence for significant heterogeneity in the estimates for most tumor markers, but we were unable to investigate underlying sources of inter-study heterogeneity because the prevalence of tumor prognostic markers was rarely presented in subgroups defined by tumor location, tumor stage, or MSI status. Between-study differences in the definitions of early- and late-onset CRC may also have contributed to heterogeneity, although we excluded studies where misclassification of early-onset CRC was apparent. Lastly, although we attempted to control for bias by performing a sensitivity analysis limited to studies that accounted for Lynch syndrome in the study design, it is possible that residual confounding by hereditary conditions or differences in tumor location may have biased the results.

5 Conclusions

In summary, early-onset CRC was associated with a lower prevalence of mutations in several oncogenes linked to mortality and poor therapeutic response, including KRAS , BRAF , and NRAS compared to individuals with late-onset disease. Conversely, early-onset disease was associated with a higher prevalence of potentially harmful mutations in TP53 and PTEN , as well as aggressive histological subtypes including mucinous and signet ring cell carcinomas. In part, these associations may reflect the higher prevalence of rectal tumors in early-onset CRC and the effect of hereditary syndromes on tumor markers. Given these findings and the alarming rise in the incidence of early-onset CRC, it is essential that clinical trials for targeted therapies enroll sufficient numbers of individuals with early-onset disease to evaluate their efficacy in this subgroup. Additional research is required to clarify the relationships with novel tumor characteristics including immune markers and to identify molecular subtypes specific to early-onset CRC that can inform treatment and prognosis.

Data availability statement

The original contributions presented in the study are included in the article/ Supplementary Material . Further inquiries can be directed to the corresponding author.

Author contributions

TL: Writing – review & editing, Writing – original draft, Visualization, Methodology, Investigation, Formal analysis, Data curation. LP: Writing – review & editing, Writing – original draft, Investigation, Data curation. SW: Writing – review & editing, Supervision, Resources, Project administration, Methodology, Funding acquisition, Conceptualization.

The author(s) declare financial support was received for the research, authorship, and/or publication of this article. This work was supported by the National Cancer Institute of the National Institutes of Health [NIH/NCI] under grants R00 CA207848 and R01 CA255318.

Conflict of interest

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Publisher’s note

All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article, or claim that may be made by its manufacturer, is not guaranteed or endorsed by the publisher.

Supplementary material

The Supplementary Material for this article can be found online at: https://www.frontiersin.org/articles/10.3389/fonc.2024.1349572/full#supplementary-material

Abbreviations

AACR, American Association for Cancer Research; APC, adenomatous polyposis coli; CI, confidence interval; CIMP, CpG island methylator phenotype; CMS, consensus molecular subtypes; COH, City of Hope (National Medical Center); CRC, colorectal cancer; EGFR, epidermal growth factor receptor; MDACC, MD Anderson Cancer Center; MSI, microsatellite instability; MSKCC, Memorial Sloan Kettering Cancer Center; MSS, microsatellite stable; OR, odds ratio; SEER, Surveillance, Epidemiology, and End Results; TIL, tumor infiltrating lymphocytes.

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Keywords: colorectal cancer, colon cancer, rectal cancer, early-onset, oncogenes, prognosis, molecular characteristics

Citation: Lawler T, Parlato L and Warren Andersen S (2024) The histological and molecular characteristics of early-onset colorectal cancer: a systematic review and meta-analysis. Front. Oncol. 14:1349572. doi: 10.3389/fonc.2024.1349572

Received: 04 December 2023; Accepted: 16 April 2024; Published: 26 April 2024.

Reviewed by:

Copyright © 2024 Lawler, Parlato and Warren Andersen. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY) . The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

*Correspondence: Shaneda Warren Andersen, [email protected]

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