Sense of Coherence as a Moderator Between Social Isolation and the Risk of Care Dependency Among Older Adults in Japan

Background/Objectives: In Japan, the rapid aging of the population has increased the need for strategies to extend healthy life expectancy and prevent care dependency. Social isolation has been identified as a major risk factor for adverse physical and psychological outcomes, but its interaction with psychological resilience factors remains unclear. This study aimed to examine the association between social isolation and the risk of care dependency among community-dwelling older adults, and to investigate whether the sense of coherence (SOC) moderates this relationship. Methods: A cross-sectional survey was conducted in City A, Kagawa Prefecture, involving 519 residents aged 65 years or older. Social isolation was assessed using the Japanese version of the Lubben Social Network Scale-6 (LSNS-6), and SOC was measured with a validated three-item scale from the University of Tokyo. The risk of care dependency was evaluated using a 15-item checklist developed by the Tokyo Metropolitan Institute of Gerontology. Nutritional status was measured using the Mini Nutritional Assessment–Short Form. Multiple imputation (m = 50) handled missing data. Standardized linear regression analyses estimated main and interaction effects, followed by robustness checks using robust, gamma, and bootstrap analyses. Results: Lower levels of social connectedness were associated with a higher risk of care dependency. A moderating trend of SOC was observed (β = 0.100, p = 0.004), suggesting that the adverse impact of social isolation may be greater among individuals with lower SOC. Conclusions: These findings suggest that SOC may play a potential buffering role mitigating the adverse effects of social isolation. Although the explanatory power of the model was moderate, the observed trends highlight the potential importance of psychosocial resources for preventive care among older adults.