Built Environments and Frailty in Older Adults: The JAGES Longitudinal Study Using Mediation Analysis

Objectives The purpose of this study was to investigate the association between subjective built environment and the onset of frailty in older adults living in the community. In addition, we examined whether daily walking time, depressive symptoms, and social support from neighbors and friends are mediating factors. Design This was a longitudinal study using prospective cohort data from the 2013 Japan Gerontological Evaluation Study. Setting and Participants Participants included 38,829 older adults who were not frail recruited from 22 cities and towns. Methods The dependent variable, frailty, was assessed using the Kihon checklist. The explanatory variables were 5 items for the subjective built environment. The mediating variables were walking time of at least 30 minutes per day, a Geriatric Depression Scale (GDS) score of at least 5 points, and social support from neighbors and friends. We performed a causal mediation analysis of mediating effects between each built environment and frailty onset. Furthermore, the proportion of mediation was estimated. Results After 3 years of follow-up, frailty emerged in 2232 adults (6.7%) in 2016. Access to parks and sidewalks, access to fresh food stores, houses or facilities where people feel free to drop in, and fascinating views, or buildings reduced the onset of frailty. Mediators significantly associated with the built environment and onset of frailty were access to parks and sidewalks (walking time: 5.9%, GDS: 22.9%, social support: 5.9%), access to fresh food stores (GDS: 31.9%, social support: 4.0%), hills and steps (GDS: 20.6%), houses or facilities where people feel free to drop in (walking time: 4.0%, GDS 28.0%, social support: 10.4%), and fascinating views, or buildings (walking time: 7.8%, GDS: 42.1%, social support: 12.0%). Conclusions and Implications We found that walking time, depression, and social support were mediating factors in the relationship between built environment and the onset of frailty.