Toward a theory-led metaframework for considering socioeconomic health inequalities within systematic reviews.

OBJECTIVES: To develop a theory-led framework to inform reviewers' understanding of what, how, and why health care interventions may lead to differential effects across socioeconomic groups. STUDY DESIGN AND SETTING: A metaframework approach combined two theoretical perspectives (socioeconomic health inequalities and complex interventions) into a single framework to inform socioeconomic health inequality considerations in systematic reviews. RESULTS: Four theories relating to complexity within systematic reviews and 16 health inequalities intervention theories informed the development of a metaframework. Factors relating to the type of intervention, implementation, context, participant response, and mechanisms associated with differential effects across socioeconomic groups were identified. The metaframework can inform; reviewer discussions around how socioeconomic status (SES) can moderate intervention effectiveness during question formulation, approaches to data extraction and help identify a priori analysis considerations. CONCLUSION: The metaframework offers a transparent, practical, theory-led approach to inform a program theory for what, how, and why interventions work for different SES groups in systematic reviews. It can enhance existing guidance on conducting systematic reviews that consider health inequalities, increase awareness of how SES can moderate intervention effectiveness, and encourage a greater engagement with theory throughout the review process.