Study design and participants
Data were obtained, between September and October 2020, from cross-sectional surveys of community-dwelling people aged ≥ 65 years without severe dependence and living in two rural areas of Japan (Gejo area in Tokamachi City, Niigata Prefecture, and Yoshijima area in Kawanishi Town, Yamagata Prefecture). On March 31, 2020, the population size (proportion) of people aged ≥ 65 years was 51,568 (39.1%) in Tokamachi and 14,901 (37.4%) in Kawanishi.Gejo in Tokamachi comprised 1,229 older adults as of September 1, 2020. After excluding 127 individuals certified with care levels 3–5 in the long-term care insurance system and 40 who had died by the date of questionnaire distribution, the questionnaire was sent to 1,062 individuals by mail and 868 returned the questionnaires (response rate: 81.7%). As we excluded 19 respondents who were not living in their own homes (e.g., currently undergoing long-term hospitalization or residing in care facilities) or provided invalid responses (e.g., a blank questionnaire) and 14 who did not respond to the question on engagement in social participation activities, 835 participants were consequently included in the analysis.Yoshijima in Kawanishi included 942 older adults as of July 31, 2020. As two older adults died before the survey commenced, we sent the questionnaires to 940 individuals by mail and received 803 completed questionnaires (response rate: 85.4%). After excluding 51 respondents who were not living in their own homes, were certified with care levels 3–5 in the long-term care insurance system, or provided invalid responses, and 63 who did not respond to the question on engagement in social participation activities, a total of 689 participants were included in the analysis.The study protocol was approved by the ethics committee of the Tokyo Metropolitan Institute for Geriatrics and Gerontology (approved on August 20, 2020) and Tohoku University Graduate School of Medicine (approved on April 12, 2020). All participants provided informed consent prior to their inclusion in the study.