Equity impact of interventions to promote physical activity in older adults: protocol for a systematic review

Due to various beneficial effects on health and well-being, physical activity is seen as one of the most important contributors to healthy aging [1]. For example, considerable evidence suggests that physical activity plays an important role in the primary and secondary prevention of major non-communicable diseases (e.g., cardiovascular diseases, type 2 diabetes mellitus, obesity, cancer, depression, chronic respiratory diseases, dementia, osteoporosis) [2‐4]. Although the benefits of regular physical activity have also been shown to be effective among older adults [5‐7], epidemiological studies suggest that physical activity level tends to decline with increasing age [8‐10].

There is also evidence indicating that physical activity is less prevalent among socially disadvantaged population groups [11‐14]. In this context, social inequalities may refer to a variety of socioeconomic, sociocultural, and sociogeographical aspects [11] which have been summarized within the PROGRESS-Plus framework proposed by the Campbell and Cochrane Equity Methods Group [15]. The acronym PROGRESS represents the following eight dimensions across which inequalities may exist: Place of residence, Race/ethnicity/culture, Occupation, Gender/sex, Religion, Education, Socioeconomic status (SES), and Social capital [16]. “Plus” considers other characteristics of populations which may be associated with social disadvantage (e.g., age or disability) [17]. With regard to older adults and physical activity, low physical activity has been shown to be associated with female sex, low SES, living in a deprived residential area, and a lack of social support [9, 10, 18‐20].

Ideally, health promotion and prevention measures should reach the whole social spectrum of a population and thus not increase social inequalities between socially advantaged and disadvantaged groups. However, there is a growing body of evidence suggesting that preventive interventions, even if they are successful at improving health behaviors or health outcomes across the population, may actually worsen inequalities between different social groups [21‐23]. According to Lorenc and colleagues, these “intervention-generated inequalities” (IGIs) are more likely to occur among interventions focusing on individual behavior changes (downstream interventions) compared to interventions focusing on social or policy changes (upstream interventions) [24]. For example, using systematic review methods, Hill and colleagues have shown that increased tobacco price has the potential to reduce smoking-related inequalities in health among adults, whereas non-targeted smoking cessation programs seem to increase inequalities [25]. The issue of IGIs has also been discussed in systematic reviews of obesity prevention interventions among adults [26, 27] and children [28], interventions to improve healthy eating [29] and school-based cognitive-behavioral [30], and health behavior interventions [31].

In the area of physical activity promotion, Humphreys and Ogilvie conducted a pilot study on how effects on social inequalities have been reported in systematic reviews and primary studies of the effects of environmental and policy interventions to promote physical activity [32]. The authors found that only few systematic reviews tended to synthesize intervention effects on social inequalities, although relevant information (e.g., on participants’ baseline characteristics, adjusted associations, subgroup intervention effects, or interaction effects) was often provided within the primary studies included in the reviews.