Systematic reviews


Reviews present, contrast, and (when appropriate) combine data across studies to address a specific question or issue related to environmental health. Reviews must utilize systematic review methodologies to identify the corpus of relevant scientific literature, including clearly defined search strategies and study eligibility criteria as needed to capture the current state of knowledge in an unbiased and comprehensive manner. A variety of review formats may be considered by EHP, such as state-of-the-science reviews, scoping reviews, evidence maps, full systematic reviews, and meta-analyses. EHP does not publish narrative reviews or reviews based on meetings (meeting summaries or reports). Regardless of review type, authors should integrate and critically analyze information from previous research, identify information gaps so as to make recommendations for future research, and draw conclusions based on the stated purpose of the review.

Note: For full systematic reviews, authors are expected to conform to appropriate guidelines, such as PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses).

Suggested length is < 10,000 words, excluding the text in the abstract, references, tables, figure legends, acknowledgments, and Supplemental Material.

Abstract: Structure using the following headings: Background, Objectives, Methods, Results, Discussion.

Introduction: Define the question or problem, and provide enough background to allow the reader to understand the importance of the review. Provide a rationale based on previous research and relevant reviews. Provide specific aims of the review with reference to study questions, including relevant population(s) and exposure(s).

Methods: For all types of reviews, including state-of-the-science reviews, provide detailed descriptions and rationales for processes used to identify the corpus of relevant scientific literature, including but not limited to:

  • Search strategy: Describe the full electronic search strategy, databases searched, and date of final search, such that the search could be fully replicated by other researchers.
  • Study eligibility criteria: Provide a detailed description of and rationale for all study inclusion/exclusion criteria, including population(s), exposure(s), evidence stream(s) (e.g., human observational, experimental animal, in vitro, etc.), date and language limitations, etc.

For systematic reviews, including scoping reviews and systematic evidence maps, include the following according to PRISMA guidelines:

  • Study selection: Describe the formal screening process used to select studies, such as number of screeners, conflict resolution, and any computer-assisted techniques (e.g., machine learning, automated text recognition).
  • Data extraction: Describe what information was extracted and how data were collected from records.
  • Study quality: Describe how the quality of individual studies, lines of evidence, or outcomes (e.g., internal validity, risk of bias) was assessed. For broad scoping reviews, study quality of individual studies is not required; however, at the very least authors should discuss at a high level the strengths/limitations of the types of studies as well as the knowledge gaps.
  • Meta-analyses (if applicable): Provide all details of statistical analyses used to synthesize data across studies, including summary measures, consistency measures, and subgroup analyses.

Results: Provide the results of study screening, summaries of extracted data, and any synthesis measures across studies using tables and figures that allow readers to draw their own conclusions rather than solely being led by the authors’ narrative.

  • Study selection: Provide numbers of studies screened and included in the review, along with reasons for exclusion at each stage. Flow diagrams (see PRISMA) are generally most effective.
  • Summary of findings: Present extracted data and study quality along with citations for each study in summary tables.
    • For broad scoping reviews, online interactive visualizations may be used to complement tables and figure within the main body of the manuscript.
    • For meta-analyses, include confidence intervals and consistency measures along with results of any additional analyses.

Discussion: Summarize the main findings for primary exposures or outcomes, and put them into context with previous related research and reviews. Discuss any limitations of the body of evidence at the exposure and/or outcome level as well as any limitations of the review process. Conclude with a brief overview of the main objectives and results of the review, including summaries of the state of the knowledge and potential knowledge gaps.