What is the role of systematic reviews in tackling health inequity?

Introduction: Enhancing health equity remains of international political importance with endorsement from the World Health Assembly in 2009. The failure of systematic reviews to consider effects on health equity is described by decision-makers as a limitation to using systematic reviews as a basis for evidence-informed decisions. Hence, there is a need for guidance on the role of systematic reviews in assessing effects on health equity.

Methods: Four studies were conducted to assess the role of systematic reviews in assessing effects on health equity. A Cochrane Collaboration methodology review and a methodology study assessed methods used in published systematic reviews to assess effects of interventions on health equity across ten categories defined by the acronym PROGRESS-Plus: Place of residence, Race/ethnicity, Occupation, Gender/sex, Religion, Education, Socioeconomic status, Social capital. Plus considers other factors associated with unequal opportunities for good health such as age, disability and developing country settings. A qualitative study assessed implementation factors that are associated with success of interventions in vulnerable populations and mapped these factors to the equity-effectiveness loop framework. An equity plausibility algorithm was developed and tested to predict the likelihood of effects of interventions on health equity.

Results: Only 13% of published systematic reviews assess effects on health equity. Four methods were used to assess effects of interventions on health equity: 1) description of people in studies; 2) description of subgroup analyses; 3) analysis of differences; and 4) applicability assessment. Only lout of 20 methodological studies used an analytic method. Implementation factors that predict success of interventions on improving health of homeless people in Ottawa mapped well onto the equity effectiveness loop framework, suggesting this framework can be used to appraise and improve interventions to promote health equity. Testing of the equity plausibility algorithm developed based on these studies showed that 67% of respondents thought that differences in relative effects of interventions were likely across sex and socioeconomic status, but there was little to no inter-rater agreement for these judgments.

Discussion: These studies show that systematic reviews lack consideration of effects of interventions on health equity. This dissertation makes recommendations to improve reporting and conduct of systematic reviews to improve the contribution of systematic reviews to the evidence-base on promoting health equity. Methodological research is needed to improve methods for assessing applicability of systematic reviews for populations across PROGRESS-Plus characteristics, by both those who conduct systematic reviews and those who use them as a basis for decision-making.