Is equity considered in systematic reviews of interventions for mitigating social isolation and loneliness in older adults?

Background: Social isolation and loneliness affect one in four older adults in many regions around the world. Social isolation and loneliness are shown to be associated with declines in physical and mental health. Intersecting social determinants of health influence both the risk of being socially isolated and lonely as well as the access and uptake of interventions. Our objective is to evaluate what evidence is available within systematic reviews on how to mitigate inequities in access to and effectiveness of interventions. Methods: We performed an overview of reviews following methods of the Cochrane Handbook for Overviews of Reviews. We selected systematic reviews of effectiveness of interventions aimed at mitigating social isolation and loneliness in older adults (aged 60 or above) published in the last 10 years. In addition, we assessed all primary studies from the most recent systematic review with a broad intervention focus. We searched MEDLINE, EMBASE, PsycINFO, CINAHL, and Scopus in collaboration with a librarian scientist. We used a structured framework called PROGRESS-Plus to assess the reporting and consideration of equity. PROGRESS-Plus stands for place of residence, race/ethnicity/culture/language, occupation, gender or sex, religion, education, socioeconomic status (SES), social capital, while "plus " stands for additional factors associated with discrimination and exclusion such as age, disability, and sexual orientation. We assessed whether PROGRESS-Plus factors were reported in description of the population, examination of differential effects, or discussion of applicability or limitations. Results: We identified and assessed 17 eligible systematic reviews. We assessed all 23 primary studies from the most recent systematic review with a broad intervention focus. All systematic reviews and primary studies described the population by one or more PROGRESS-Plus factor, most commonly across place of residence and age, respectively. None of the reviews and five primary studies examined differential effects across one or more PROGRESS-Plus dimension. Nine reviews and four primary studies discussed applicability or limitations of their findings by at least one PROGRESS-Plus factor. Conclusions: Although we know that social isolation and loneliness are worse for the poorest and most socially disadvantaged older adults, the existing evidence base lacks details on how to tailor interventions for these socially disadvantaged older people.