Regional Differences in Disability Incidence among Japanese Adults Aged 75 Years and Older: A 4-Year Prospective Cohort Study

The present prospective study investigated the regional differences and trajectories of new-onset disabilities among older adults in the districts within a city in Japan. We analyzed data from 5050 Japanese residents aged ≥75 years old (men/women: 2512/2538) who completed the Kihon Checklist (a self-reported questionnaire on frailty) and a questionnaire on medical history and social capital in Ikoma city in 2015. The incidence of disability was determined using the new certification of long-term care insurance and was followed-up on 4 years after the primary outcome. A Cox proportional hazards regression model was used to determine the factors related to the risk of incident disability. During the 4-year follow-up period, 567 participants (11.2%) were newly certified to have a disability. The disability incidence rate ranged from 8.1% to 14.6%, depending on the district. After adjustment for the covariates of: older, women, stroke, prefrail, frail, participation in multiple social activities (hazard ratio [HR] = 0.72, 95% confidence interval [CI] = 0.56–0.91), and one of the districts (HR = 1.67, 95% CI = 1.06–2.61) were significantly associated with disability incidence. The findings of this longitudinal study suggest that there could be a regional difference in disability incidence among older adults in Japan. Thus, community-based approaches should be designed to prevent disability in older adults.