Dynamic frailty trajectories, multidimensional resilience, and risk of incident hip fracture: A prospective cohort study with competing risk analysis.

BACKGROUND

Hip fractures represent a major public health challenge in aging populations. While frailty is a recognized risk factor, evidence regarding the protective association of multidimensional resilience trajectories remains insufficient.

METHODS

Data from five waves of the China Health and Retirement Longitudinal Study (CHARLS, 2011-2020), including 7105 participants aged ≥ 60. A multidimensional resilience index (MDRI) was quantified via the system-level residual method. Latent Class Growth Modelling (LCGM) identified dynamic trajectories of frailty and resilience. Fine-Gray models evaluated their associations with incident hip fracture risk, treating death as a competing risk.

RESULTS

Three frailty trajectories were identified: Low-Stable (53.4%), Moderate-Rising (21.2%), and High-Rising (25.4%). Compared to Low-Stable, both Moderate-Rising (SHR = 1.48; 95% CI: 1.11-1.97; P = 0.007) and High-Rising (SHR = 1.50; 95% CI: 1.13-1.99; P = 0.005) groups increased fracture risks, suggesting a risk plateau during frailty acceleration. High-level MDRI trajectories showed a potent independent protective association (SHR = 0.44; 95% CI: 0.30-0.64; P < 0.001). This protection was robust across sex and socioeconomic subgroups (Pinteraction > 0.05).While consistent across age groups (Pinteraction = 0.177), the association was more pronounced in individuals aged < 75 years (SHR = 0.42; 95% CI: 0.27-0.67).

CONCLUSIONS

Rising frailty trajectories, rather than baseline status alone, are strong predictors of incident hip fractures. MDRI confers a robust and independent protective association, reducing fracture risk by 56%. Fracture prevention strategies should move beyond static risk assessments towards monitoring the dynamic acceleration of frailty and actively promoting resilience-building assets in older populations.