Association of community-level social capital with dementia: A multilevel nine-year longitudinal study using data...

Individual-level social capital prevents cognitive decline. However, a few studies have focused on the effects of community-level social capital on dementia. Therefore, we investigated the association between community-level social capital and dementia onset based on longitudinal study data on older adults in Japan.

We used longitudinal data from the Japan Gerontological Evaluation Study, obtained over nine years (2010-2019). In total, 35,921 physically and cognitively independent individuals (16,848 males and 19,073 females) aged ≥65 years and nested within 308 communities in seven municipalities participated in the study. Dementia onset was assessed using the public long-term care insurance registration. Social capital was assessed using three dimensions: civic participation, social cohesion, and reciprocity. We performed a two-level multilevel survival analysis stratified by sex, calculated hazard ratios (HRs), and 95% confidence intervals (CIs).

During the follow-up, 6245 (17.4%) dementia onset cases were identified. The cumulative incidence of dementia was 16.2% in males and 18.4% in females. After adjusting for covariates, individual-level civic participation was associated with a lower incidence of dementia in both males and females (HR, 0.84; 95% CI, 0.77-0.92; HR, 0.78; 95% CI, 0.73-0.84). Community-level civic participation and social cohesion were associated with a lower incidence of dementia among females (HR, 0.96; 95% CI, 0.93-0.99; HR, 0.93; 95% CI, 0.88-0.98) and cross-level interaction on social cohesion among females (HR, 0.95; 95% CI, 0.90-0.99).

Living in a community with high civic participation and social cohesion is associated with a lower incidence of dementia among older females. Therefore, promoting civic participation and social cohesion in the community may be a useful population-based strategy to delay or prevent the onset of dementia.