Comparison of the Incidence of Functional Disability Correlated With Social Participation Among Older Adults in Japan.

BACKGROUND:Japan, which has the world's longest life expectancy, has been reporting rejuvenation of physical function among its older adult population. However, evidence for the incidence of functional disability is limited. This study aimed to investigate the comparison in the incidence of functional disability. DESIGN:We used data from the Japan Gerontological Evaluation Study. SETTING AND PARTICIPANTS:The participants were 2 nonoverlapping cohorts of 22,522 (2010-2013 cohort) and 26,284 (2016-2019 cohort) individuals aged 65 years and older from 5 municipalities who were followed for 3 years each. METHODS:The incidence rates of functional disability during the 3-year follow-up period were compared between cohorts. To examine the incident differences between the cohorts, we adjusted for social participation and 9 additional factors that would be expected to improve with social participation using the Weibull survival models adjusting for municipalities as random effects. The analysis was stratified by age groups (65-74 years old and ≥75). RESULTS:The incidence rate of functional disability per 10,000 person-years decreased from 68.6 (2010-2013 cohort) to 51.4 (2016-2019 cohort) in the 65 to 74 years old group and 380.0 (2010-2013 cohort) to 282.6 (2016-2019 cohort) in the ≥75 group; the hazard ratios (95% CIs) were 0.75 (0.64-0.89) and 0.73 (0.67-0.80), respectively. However, these significant decreases disappeared with adjustments for social participation and additional factors. CONCLUSIONS AND IMPLICATIONS:The incidence of functional disability decreased in a recent cohort, which may be explained by social participation and possibly related factors. Promoting social participation could contribute to a decreasing incidence of functional disability among older adults.