Social Frailty and Functional Status in Japanese Older Adults: The Mediating Role of Subjective Cognitive Function

Objective This study aimed to explore the direct and indirect effects of social frailty on functional state trajectories mediated by subjective cognitive function in older adults. Design Longitudinal study. Setting and Participants Overall, 514 adults aged ≥65 years living in a suburban area of central Japan were included in this study. Methods Five-item social frailty index (going out, visiting, feeling helpful, living alone, and talking to others), subjective cognitive function from the Kihon Checklist, and instrumental activities of daily living disability. Latent growth curve models were applied to examine the longitudinal relations among the variables. Results During the 6-year follow-up in latent growth curve models, the initial level of social frailty in older adults was negatively associated with that of functional status (β = −0.53, P < .001), and the rate of change in social frailty was negatively associated with that in functional status (β = −0.78, P < .001). In the mediation model, the indirect effect from the social frailty level to functional status level through subjective cognitive function level was significant (β = −0.14, 95% CI −0.29, −0.09); the rates of change in subjective cognitive function mediated the relationship between those in social frailty and functional status (β = −0.35, 95% CI –0.46, −0.25). Conclusions and Implications This study found that there is an association between social frailty and functional status in Japanese older adults. Subjective cognitive function mediated this relationship. Hence, additional research is required to investigate additional potential factors linking social frailty and functional status in order to gain a better understanding of the underlying mechanisms.