Dynamic frailty changes, cumulative frailty index, and the risk of stroke: Evidence from the China health and retirement longitudinal study.

This study aimed to investigate the association between dynamic changes in frailty status, cumulative frailty index (FI), and the risk of incident stroke, providing novel evidence to inform stroke prevention strategies. This prospective study used data from the China health and retirement longitudinal study. Frailty transitions across 2 waves were classified into 7 patterns: stable robust, robust to pre-frail/frail, stable pre-frail, pre-frail to robust, pre-frail to frail, stable frail, and frail to pre-frail/robust. Multivariable Cox models estimated stroke risk for each transition, with "stable robust" as the reference. The cumulative FI was assessed categorically (quartiles) and continuously (per standard deviation increase). Restricted cubic splines evaluated dose-response associations. Subgroup and sensitivity analyses tested robustness. Among 6947 participants (median follow-up 7 years), stroke risk varied markedly by frailty transition. Compared with stable robust, the stable frail group showed the highest risk (hazard ratio [HR] = 4.48; 95% confidence interval [CI]: 3.25-6.18). Robust to pre-frail/frail transitions increased risk by 81% (HR = 1.81; 95% CI: 1.31-2.50). Relative to stable pre-frail, improving to robust was protective, whereas transition to frail increased risk by 58% (HR = 1.58; 95% CI: 1.24-2.01). Compared with stable frail, improvement to pre-frail/robust reduced risk (HR = 0.60; 95% CI: 0.43-0.84). The cumulative FI showed a strong linear association with stroke: each 1 - standard deviation increase was associated with a 55% higher risk (HR = 1.55; 95% CI: 1.45-1.65), and participants in the highest versus lowest quartile had over 3-fold higher risk (HR = 3.29; 95% CI: 2.59-4.17). Worsening frailty status substantially elevates stroke risk, whereas frailty improvement confers measurable protection. Cumulative FI is linearly associated with incident stroke, underscoring the importance of early identification and long-term management of frailty in stroke prevention.