Social Frailty and Happiness Among Older Adults in a Semi-Rural Japanese Community: A Cross-Sectional Study in Fujikawaguchiko

Compared to physical frailty, social frailty (SF), the erosion of social resources, activities, and self-management has been relatively less studied, and its link with happiness in rural microgeographical settings is unclear. We surveyed 312 adults aged ≥ 65 years in Fujikawaguchiko, Japan, and analyzed 19 indicators spanning participation, interaction, neighborhood environment, and living arrangements. Principal component analysis indicated three facets (active social participation, neighborhood connectedness, and social interaction frequency) that explained 42% of the variance. Propensity scores for SF were estimated from sociodemographic and health covariates, and stabilized inverse probability weight-adjusted linear models were used to predict self-reported happiness. Neighborhood connectedness and local support were consistently associated with higher levels of self-reported happiness. This association was weaker in sparsely-populated mountain zones. Under a stricter definition of frailty, social interaction frequency also predicted higher self-reported happiness. The main findings were consistent across the weighting schemes and model specifications. Neighborhood connectedness and reliable local support have emerged as central to the happiness of older rural adults, although their benefits may be attenuated by low population densities. Locally-tailored interventions that foster trust and meaningful engagement can promote healthy aging. Further studies are required to confirm the causality and cultural generalizability of these findings.