Objectives: The Short Form 12 Survey (SF-12) three-component model is used to compute health-related quality of life (QoL): it includes physical, mental, and role-social QoL. We asked whether the SF-12 three-component model is associated with disability-free survival. Methods: People ≥65 years old were included (n = 2634). SF-12 scores were assessed at baseline. The outcome was a composite of loss of independence (LoI) and death. LoI was defined using Japan's long-term care insurance categories. Hazard ratios (HRs) for LoI or death were estimated using Cox proportional hazards models. Results: Better physical QoL was inversely associated with LoI or death (adjusted HR per 10-point increase: .88 [95% CI: .81-.96]), but mental QoL was not. Better role-social QoL was inversely associated with LoI or death only among participants with higher than average physical QoL (adjusted HR per 10-point increase: .79 [95% CI: .65-.96], p for interaction = .04). Discussion: Physical QoL was associated with disability-free survival, and role-social QoL was associated with disability-free survival among those with better physical QoL.
Keywords: SF-12; cohort; death; loss of independence; quality of life.