Physical frailty and functional resilience after hip fracture in older adults: a risk-set matched longitudinal study

BACKGROUND: Functional trajectories after hip fracture vary widely; whether physical frailty amplifies excess decline or instead marks poorer functional prognosis remains unclear. OBJECTIVES: To distinguish these roles of physical frailty after hip fracture. DESIGN: Population-based cohort study with risk-set matching and a case-only prognostic analysis. SETTING: Community-based, China. PARTICIPANTS: Adults aged at least 60 years participating in the China Health and Retirement Longitudinal Study, 2011-2020. MEASUREMENTS: Hip-fracture cases were matched to up to 4 same-wave fracture-free comparators. Preceding-wave physical frailty was assessed using an adapted Fried score (0-5). Matched models estimated fracture-associated excess activities of daily living (ADL) and instrumental activities of daily living (IADL) change and Fried-score interactions; case-only models estimated the probability of being alive with ADL maintained at or returned to the pre-event level at the next survey. RESULTS: The analysis included 252 cases (mean age at the first fracture-report interview, 70.6 years; 132 [52.4%] women) and 1005 comparator records. Relative to matched comparators, hip fracture was associated with greater ADL and IADL deterioration, with average excess increases of 0.73 difficulties in ADL (95% confidence interval [CI], 0.47 to 0.99) and 0.31 difficulties in IADL (95% CI, 0.09 to 0.53). The ADL contrast did not clearly vary by Fried score (interaction per criterion, 0.03; 95% CI, -0.28 to 0.34). Among cases, the adjusted probability of being alive with ADL maintained at or returned to the pre-event level declined from 72.9% at Fried score 0 to 46.4% at score 3 (risk difference, -26.5 percentage points; 95% CI, -50.3 to -2.8). CONCLUSIONS: Physical frailty was associated with poorer functional prognosis, whereas evidence that it modified fracture-associated excess decline was unclear. Functional assessment should span frailty levels; frailty may inform support and follow-up intensity but should not determine rehabilitation access.