Combined Impacts of Physical Activity, Dietary Variety, and Social Interaction on Incident Functional Disability in Older Japanese Adults

BACKGROUND: This 3.6-year prospective study examined combined impacts of physical activity, dietary variety, and social interaction on incident disability and estimated population-attributable fraction for disability reduction in older adults. METHODS: Participants were 7,822 initially non-disabled residents (3,966 men and 3,856 women) aged 65–84 years of Ota City, Tokyo, Japan. Sufficiency of moderate-to-vigorous-intensity physical activity (MVPA) ≥150 min/week, dietary variety score (DVS) ≥3 (median), and social interaction (face-to-face and/or non-face-to-face) ≥1 time/week was assessed using self-administered questionnaires. Disability incidence was prospectively identified using the long-term care insurance system’s nationally unified database. RESULTS: During a follow-up of 3.6 years, 1,046 (13.4%) individuals had disabilities. Independent multivariate-hazard ratios (HRs) and 95% confidence intervals (CIs) of MVPA, DVS, and social interaction sufficiency for incident disability were 0.68 (95% CI, 0.59–0.78), 0.87 (95% CI, 0.77–0.99), and 0.90 (95% CI, 0.79–1.03), respectively. Incident disability HRs gradually reduced with increased frequency of satisfying these behaviors (any one: HR 0.82; 95% CI, 0.65–1.03; any two: HR 0.65; 95% CI, 0.52–0.82; and all three behaviors: HR 0.54; 95% CI, 0.43–0.69), in an inverse dose-response manner (P < 0.001 for trend). Population-attributable fraction for disability reduction in satisfying any one, any two, and all three behaviors were 4.0% (95% CI, −0.2 to 7.9%), 9.6% (95% CI, 4.8–14.1%), and 16.0% (95% CI, 8.7–22.8%), respectively. CONCLUSION: Combining physical activity, dietary variety, and social interaction substantially enhances the impacts on preventing disability among older adults, with evidence of an inverse dose-response manner. Improving insufficient behavior elements through individual habits and preexisting social group activities may be effective in preventing disability in the community.