Dose-Responsive Impacts of Social Frailty on Intrinsic Capacity and Healthy Aging among Community-Dwelling Middle-aged and Older Adults: Stronger Roles of Social Determinants over Biomarkers

Objective: The intricate relationship between social determinants, e.g., social frailty, biomarkers and healthy aging remains largely unexplored, despite the potential for social frailty to impact both intrinsic capacity (IC) and functional ability in the aging process. Design: Retrospective longitudinal cohort study. Setting and Participants: Participants aged 50+ years from the Social Environment and Biomarkers of Aging Study (SEBAS) in Taiwan, stratified into three age groups: 50–64, 65–74 and 75+. Measurements: Social frailty was defined based on a score derived from four domains: exclusion from general resources, social resources, social activity, and fulfillment of basic social needs. The scores were categorized as score=0 (no social frailty), 1 (social pre-frailty), and 2+ (social frailty). Multivariable logistic regression and Cox proportional hazard models were employed to examine the dose-responsive relationship between social frailty, low IC, functional and psychological health, and mortality. Results: Of 1015 study participants, 24.9% and 7.9% were classified as social pre-frailty and social frailty, respectively. No significant differences were observed in most biomarkers between those with social frailty and those without. A dose-responsive relationship was found between social frailty and increased risk of low IC (social pre-frailty: aOR 2.20 [95% CI 1.59–3.04]; social frailty: 5.73 [3.39–9.69]). Similar results were found for functional and psychological health. However, no significant association between social frailty and all-cause mortality was found at the 4-year follow-up (social pre-frailty: aHR 1.52 [95% CI 0.94–2.43]; social frailty: 1.59 [0.81–3.09]). Conclusions: The significant association between social frailty and low IC, functional limitations, cognitive declines, and depressive symptoms underscores the pressing need for research on intervention strategies to enhance healthy aging in the lifespan course.