Longitudinal trajectories of social frailty and the risk of all-cause mortality among older adults in South Korea: Exploration of the mediating role of cognitive functioning

BACKGROUND: Mounting evidence indicates that social frailty leads to adverse health outcomes in older adults. However, longitudinal trajectories of social frailty and their relationship with all-cause mortality have not been fully investigated. We analyzed the association between social frailty trajectories and all-cause mortality, and the mediating role of cognitive functioning in this relationship. METHODS: A nationally representative sample of older adults in South Korea was analyzed (n = 5,941). Social frailty was measured multidimensionally through social activity, social networks, social support, loneliness, and living alone. Social frailty trajectories from 2006 to 2014 were identified using a growth mixture model. Subsequent change in cognitive functioning was assessed using the Mini-Mental State Examination. Participants were then followed for all-cause mortality through 2022. Cox regression was employed to assess the relationship between social frailty trajectory and all-cause mortality, using hazard ratios (HRs) and 95% confidence intervals (CIs). Mediation analysis was performed to assess the mediating role of poor cognitive functioning. RESULTS: Two social frailty trajectories were identified: stable-low trajectory (n = 5,065, 85.3%) and high-increasing trajectory (n = 876, 14.7%). Compared to the stable-low social frailty trajectory, the high-increasing social frailty trajectory was linked to an elevated risk for all-cause mortality (HR = 1.32; 95% CI = 1.11-1.57). Subsequent poor cognitive functioning partially accounted for the excess hazard of all-cause mortality among those experiencing a high-increasing social frailty trajectory (proportion mediated: 20.8%, 95% CI: 10.5%-59.5%). CONCLUSIONS: Experiencing an increasing social frailty trajectory was linked to elevated mortality risk in older adults, and subsequent poor cognitive functioning partially accounted for this association.