Social isolation and mortality risk in late-stage older Japanese: A longitudinal study of community-dwelling residents from 2020 to 2024

Abstract

Objectives To examine the association between social isolation and mortality among older adults aged [≥]75 years in Japan. Study design A retrospective longitudinal study included homebound Japanese adults aged [≥]75 years who participated in voluntary health checkups conducted by Zentsuji City, Kagawa Prefecture, Japan, between 2000 and 2024. Methods The relationship between social isolation and mortality was assessed using the Cox proportional hazards model. Social isolation was defined as the absence of regular contact with family or friends, and survival information was confirmed in the city's database as of 1 July 2024. Results Of the 3366 participants (male: 42.4%), 3024 (male: 42.6%) remained in the final cohort. At study entry, socially isolated participants tended to be older, less likely to exercise, have worse self-rated health and life satisfaction, and have no family members in the same household. The mean follow-up time was 2.47 years, during which 9.1% of the participants died. Mortality risk was 2.37 times higher (95% confidence interval [CI]: 1.61-3.48) for socially isolated individuals than for those who were not socially isolated, after controlling for covariates such as physical status, self-rated health, lifestyle, life satisfaction, and sharing a household with family members. The results showed a consistent trend, even after excluding participants with short follow-up periods. Conclusion Based on data from older adults in Japan, a population with the world's longest life expectancy, the findings of this study may help guide public health interventions aimed at reducing social isolation in today's globally aging society.