Social Frailty and Functional Disability: Findings From the Singapore Longitudinal Ageing Studies

To examine the association between the social frailty (SF) phenotype and functional disability, independently of the physical frailty (PF) phenotype, and compare the abilities of the PF, SF, and combined social and physical (PSF) indexes for predicting functional disability.Cross-sectional and longitudinal analyses of a population-based cohort (Singapore Longitudinal Ageing Study, SLAS-1) of 2406 community-dwelling older adults with 3 years of follow-up (N = 1254 and N = 1557 for instrumental activity of daily living (IADL) disability and severe disability (≥3 basic ADL) respectively).Seven-item social frailty index (living arrangements, education, socioeconomic status, and social network and support, 0 = nil SF, 1 = low, 2-7 = high), PF phenotype (Fried criteria), and instrumental activities of daily living (IADLs) disability and severe disability (≥3 basic ADLs).Compared to nil SF, low and high SF were significantly associated with 1.3 to 2.4 fold increased prevalence and incidence of IADL disability, and 6.3 fold increase in severe disability. Frail individuals with and without SF stood out with 5-11 fold increased prevalence and incidence of IADL disability and 21-25 fold increased prevalence and incidence of severe disability, compared to robust individuals without SF. A combined PSF index more accurately identified individuals with increased risk of functional disability (ROC = 64%) and severe disability (ROC = 81%) than either the SF or the PF indexes alone (55% to 68%).The SF index alone or in combination with the PF index has clinical relevance and utility for identifying and stratifying older people at risk of disability. The mental frailty construct is closely related to SF and should be further investigated in future studies.