Impact of universal interventions on social inequalities in physical activity among older adults: an equity-focused systematic review

Background: Physical activity is one of the most important contributors to healthy aging. Public health strategies aiming to promote physical activity among older adults are increasingly being implemented. However, little is known about their impact on social inequalities. Purpose of the study was to analyze whether and how studies of interventions consider effects on social inequalities in physical activity among older adults. Methods: Nine electronic databases were searched to identify quantitative studies evaluating the effects of interventions on self-reported or objectively measured physical activity among the general population of older adults (>= 50 years). English and German language peer-reviewed journal articles published between 2005 and 2015 were included. Using the PROGRESS-Plus framework, data on whether and how social factors were considered both for describing participants' baseline characteristics and for measuring intervention effects were systematically extracted. Studies examining differential intervention effects by at least one PROGRESS- Plus factor were quality assessed. Results were presented in narrative synthesis. Results: Fifty-nine studies were included. Beside age and sex, 44 studies used at least 1 further PROGRESS-Plus factor for the description of participants' baseline characteristics. When measuring intervention effects, 22 studies considered PROGRESS-Plus factors as control variables. Eleven studies reported having analyzed potential effects on inequalities by testing interaction effects, stratifying effect analyses, or exploring associations between PROGRESS-Plus factors and increases in physical activity following an intervention. Effects were most often analyzed by gender/sex (n = 9) and age (n = 9), followed by education (n = 3), marital status (n = 2), and race/ethnicity (n = 2). Five studies pointed to gender/sex-or age-specific intervention effects, indicating that some interventions affect males and females, and younger and older individuals differently. Conclusions: Many studies evaluating the effects of interventions on physical activity among older adults have not exploited the potential for assessing effects on social inequalities so far. There is an urgent need for systematic application of appropriate methodological approaches and transparent reporting of social inequalities-related findings which can provide important indications for the design of those interventions most likely to be effective across all social groups of older adults.