Municipal Progress in Community Building and Subsequent Individual Social Capital Among Older Adults in Japan: A Multilevel Longitudinal Study

Healthy ageing requires supportive environments beyond individual behaviors. Community building has gained policy attention, but evidence on how municipal progress in community building relates to individual social capital remains limited. We analyzed data from 91,891 older adults aged ≥ 65 years across 49 municipalities in Japan using the Japan Gerontological Evaluation Study (2019–2022). We examined whether municipal community-building progress in 2020 related to subsequent individual structural and cognitive social capital in 2022, after adjusting for individual-level covariates and social capital in 2019 and municipal-level covariates in fiscal year 2019. We applied multilevel linear regression with individuals nested within municipalities and assessed heterogeneity using a moderator-wide approach. Higher preventive care and daily life support scores and a greater number of community gathering places per 1000 older adults related to higher structural social capital. These associations were consistent across most subgroups, although the association between the number of community gathering places per 1000 older adults and structural social capital was stronger in municipalities with smaller older populations. We found no clear overall association between municipal community-building indicators and cognitive social capital. However, higher living support system scores related to higher cognitive social capital among women and adults aged ≥ 75 years. Municipal community-building efforts related differently to structural and cognitive social capital. Participation-oriented measures showed consistent associations with structural social capital, whereas support-oriented measures related to cognitive social capital more selectively. These findings highlight the importance of aligning community-building strategies with both social capital dimensions and population characteristics to promote healthy ageing.