Table 1

Inclusion and exclusion criteria

PopulationParticipants from the general population and assessed for the presence of multiple chronic conditions (multimorbidity).Participants initially selected based on the presence of index diseases (ie, studies of comorbidity). Participants from solely institutionalised care settings (eg, nursing homes). Participants solely young people (age <18 years).
ExposureStudy exposure(s) included at least one household or area-level SDoH that aligns with factors from the World Health Organisation (WHO) Commission on SDoH (CSDH) Framework9 and the idea that SDoH are ‘causes of the causes’ of ill-health20 (eg, household income or area-level deprivation).Study exposure(s) include individual SDoH only (eg, ethnicity). Study exposure(s) are direct “causes” of ill-health, such as health behaviours (eg, smoking), or are factors associated with the health system itself (eg, access to services).
ComparatorStudy reports comparator group(s) for SDoH exposure(s) (eg, what is the prevalence of multimorbidity for those in the lowest vs the highest household income groups).Study does not report a comparator group for SDoH exposure(s).
OutcomeAssess multimorbidity burden (prevalence or incidence studies).Assignment to multimorbidity patterns or trajectories. Measures of multimorbidity severity (eg, indices used weighted by disease severity).
Study designPeer-reviewed studies of quantitative research designs (cross-sectional and longitudinal).Systematic reviews, meta-analyses and qualitative research (citations of relevant reviews searched).