Social Frailty Components and Mortality in Korean Older Adults Controlling for Physical Frailty: Analysis of the Korean Longitudinal Study of Ageing(2006-2024)

Abstract

This study examined whether social frailty operates as a single construct or whether its components differ in their association with mortality among Korean older adults. Using the Korean Longitudinal Study of Ageing (KLoSA, 2006–2024), 4,164 adults aged 65 or older at baseline were followed. Mortality excluding external causes (injury and accidents), which are unlikely to reflect social aging, was modeled with Cox proportional-hazards regression. Social frailty was measured by five components-social support deficit, low social activity, weak social network, loneliness, and living alone-and each component was tested for its independent association with mortality in both separate and simultaneous models, after adjustment for sociodemographic and health covariates and physical frailty. In separate models, low social activity (HR 1.14), social support deficit (HR 1.15), and weak social network-infrequent contact with close friends (HR 1.25)-each independently predicted mortality after controlling for physical frailty. When the five components were entered simultaneously, social support deficit (HR 1.14) and weak social network (HR 1.21) remained independent predictors, whereas low social activity attenuated as it shares the social-participation dimension with friend contact. In contrast, loneliness and living alone showed no significant association once physical frailty was controlled. Conclusions were robust across multiple-comparison correction, alternative death definitions, competing-risk, missing-data analyses. These findings indicate that social frailty is not a monolithic construct; what most strongly explainsmortality among older adults is disengagement from social participation and the absence of social support. Beyond physically oriented frailty screening, assessment and intervention should incorporate social participation and support, focusing on the functional content of relationships rather than living arrangements.