Consideration of health inequalities in systematic reviews: a mapping review of guidance

BACKGROUND: Given that we know that interventions shown to be effective in improving the health of a population may actually widen the health inequalities gap while others reduce it, it is imperative that all systematic reviewers consider how the findings of their reviews may impact (reduce or increase) on the health inequality gap. This study reviewed existing guidance on incorporating considerations of health inequalities in systematic reviews in order to examine the extent to which they can help reviewers to incorporate such issues. METHODS: A mapping review was undertaken to identify guidance documents that purported to inform reviewers on whether and how to incorporate considerations of health inequalities. Searches were undertaken in Medline, CINAHL and The Cochrane Library Methodology Register. Review guidance manuals prepared by international organisations engaged in undertaking systematic reviews, and their associated websites were scanned. Studies were included if they provided an overview or discussed the development and testing of guidance for dealing with the incorporation of considerations of health inequalities in evidence synthesis. Results are summarised in narrative and tabular forms. RESULTS: Twenty guidance documents published between 2009 and 2016 were included. Guidance has been produced to inform considerations of health inequalities at different stages of the systematic review process. The Campbell and Cochrane Equity Group have been instrumental in developing and promoting such guidance. Definitions of health inequalities and guidance differed across the included studies. All but one guidance document were transparent in their method of production. Formal methods of evaluation were reported for six guidance documents. Most of the guidance was operationalised in the form of examples taken from published systematic reviews. The number of guidance items to operationalise ranges from 3 up to 26 with a considerable overlap noted. CONCLUSIONS: Adhering to the guidance will require more work for the reviewers. It requires a deeper understanding of how reviewers can operationalise the guidance taking into consideration the barriers and facilitators involved. This has implications not only for understanding the usefulness and burden of the guidance but also for the uptake of guidance and its ultimate goal of improving health inequalities considerations in systematic reviews.