Evidence synthesis without equity: a missed opportunity to promote health and improve health care

For 20 years, proponents of evidence reviews have bemoaned the absence of an equity perspective in systematic reviews. In 2006, the Cochrane and Campbell Collaborations announced the formation of a new combined “research field” that would aim “to assess the effect of interventions on health disparities and health equity.”1(p.1128) Since then, many tools, guides, and tutorials have been produced (eg, PROGESS/+ and PRISM-Equity, the EPPI Centre guidance, Cochrane Evidence Synthesis and Methods Group tutorial) but, nearly 20 years after Lofti and colleagues2 insisted that evidence synthesis must “take into account equity considerations in a systematic and explicit manner, regardless of how equity was addressed in the original research,”(p.2) this has not yet been achieved. For example, Kunonga et al.3 identified only 62 reviews out of the 5294 records considered (1.2%) that fulfilled their criteria (ie, focused on health intervention, considered equity, and used a methodological guide to support this). Change is required in 4 areas if evidence reviews are to take equity seriously some aspects of which were noted by Pettecrew and Roberts: methodological, conceptual, power, and translational.4 These are summarized in Table 1; few are new, but all bear reiteration. Table 1: - Maximizing the contribution of evidence reviews to health equity Area of focus Changes required Methodological Integrate equity across the review process Avoid average impacts Review literature on social and commercial determinants of health equity Ensure review questions ask for whom does [an intervention/action] work, under what conditions, and why? Don’t just describe distributional effects; explore why they are distributed as they are Conceptual Focus on topics that are likely to have most impact on health equity Extend beyond health care to include social determinants such as including housing, employment, and social security Use political economy framing Power Ask “who benefits, who loses, and who decides?” in relation to any topic being reviewed Involve communities living in disadvantage in the review team and across the review processes Translation Aim to disseminate to a wide audience, including the public Consider human rights, redistribution, and regulatory aspects of the evidence Methodologically, reviews need to integrate equity across the process, not treat it as an afterthought. Equity should shape the review questions and inclusion criteria, underpin the synthesis, and frame the interpretation and recommendations. The FOREQUITY online resource (https://forequity.uk) explicitly supports this integration, but it also requires evidence reviews to be based on a theory of change that takes equity into account. Utilizing the questions underpinning realist evaluation5 could help focus a review firmly on equity, asking “For whom does [this intervention] work, under what conditions, and why?” Petticrew et al.6 argued that these questions are central to equity reviews, as their purpose is to explore the distribution of any effects identified. But we would add that these reviews must move beyond description to explore the reasons for the effects. Too often the inclusion criteria chosen exclude populations living in the most disadvantaged circumstances. Despite repeated calls for reviews to broaden the evidence included, randomized controlled trials and other controlled designs are still privileged. We know that these designs can exclude people with comorbidities, those experiencing insecure housing and/or employment, those facing language barriers, or those with limited education. These controlled studies rarely reflect real-world contexts or deal with the complex and interacting drivers of inequities.7,8 The extent of these mainstream methodological errors have been described as epistemic injustice.9 Conceptually, agencies such as JBI, who support the production of evidence reviews, state their aim as producing evidence to promote health. However, to achieve this aim, the focus can’t be only on health care and health policy. Reviews must also look at the range of policy interventions that are most powerful in promoting health. The World Health Organization sees social determinants of health (SDoH) as making a significantly greater contribution to health gain than health care.10 These include structural and commercial determinants of health, such as labor market practices, housing, education systems, regulatory, fiscal, and non-health policy interventions. While more reviews are focusing on SDoH,11 they remain a minority. In 2022, only 1.3% of the 8922 reviews in the Cochrane Library addressed SDoH topics.2 Whatever the topic, addressing inequities in reviews requires close attention to questions of power. A political economy of health perspective provides a strong conceptual base for this. Evidence reviews tend not to ask “who benefits, who loses, and who decides?” Yet, answers to these questions are vital in determining who has access to care and the wider structural determinants of health. Institutional, colonial, or commercial power are vital in determining these access issues. For Indigenous peoples, the ongoing effects of colonialism significantly affect access to health care and health. The extent to which health systems are publicly funded and run or privately organized has a big impact on health. More reviews need to consider these crucial implementation factors. In addition, evidence reviews are typically controlled by researchers. There has been progress involving people with lived experience in reviews, but their influence is often limited,12 and the most marginalized groups—including Indigenous peoples; communities living in racial, socioeconomic, or disability disadvantage; or social justice movements—are rarely involved. Involving these groups in framing questions, interpreting findings, and crafting recommendations would likely strengthen the equity focus. Finally, more attention needs to be given to the audience for evidence reviews. Currently, many are not well suited to policymakers, civil society, or the media. Additionally, translation rarely considers the implications of the findings in terms of human rights, the opportunities for redistribution, or regulation to shape outcomes to be equitable. Evidence reviews have an important role to play in working for greater equity but, currently, they fall well short of this potential. More reviews focusing on social determinants are required. Equity needs to be integrated across the review process, equity-sensitive theories of change need to underpin the review, and reviews need to ask questions about who is benefitting and who is losing out. If they were able to do this, then the results would stand a chance of contributing to a reduction of health inequities rather than, at best, having no impact or, at worse, widening inequalities.