Triglyceride–Glucose Index Combined with Frailty Index and Incident Stroke in Older Chinese Adults with Arthritis: A Prospective Cohort Study

<title>Abstract</title> <p> <bold>Introduction</bold> : Conventional stroke risk models inadequately capture metabolic and biological vulnerability in aging populations with chronic inflammatory conditions. This study examined whether the triglyceride–glucose–frailty index (TyGFI), integrating insulin resistance and deficit accumulation, predicts incident stroke in Chinese adults with arthritis. <bold>Methods</bold> : We analyzed 3,649 participants aged ≥ 45 years with physician-diagnosed arthritis and no prior stroke from the China Health and Retirement Longitudinal Study (2011–2020), followed for a median of 9 years. TyGFI was calculated as the product of the triglyceride–glucose index and a 40-item frailty index. Cox proportional hazards models estimated hazard ratios (HRs) and 95% confidence intervals (CIs), with sequential adjustment for demographics, lifestyle, and body mass index (BMI). Nonlinearity was assessed using restricted cubic splines. <bold>Results</bold> : During follow-up, 398 participants (10.9%) developed incident stroke. Each 1-standard deviation increase in TyGFI was associated with a 33% higher stroke risk (HR 1.33, 95% CI 1.22–1.47). A significant nonlinear relationship was observed (P = 0.001), with a steeper risk increase below TyGFI = 54.62 (HR 2.44, 95% CI 1.64–3.62) than above it (HR 1.18, 95% CI 1.04–1.34). Compared with the lowest tertile, the highest tertile showed a 2.15-fold higher risk (95% CI 1.63–2.82). Associations remained robust in sensitivity analyses. <bold>Conclusion</bold> : Higher TyGFI was independently associated with increased incident stroke risk in Chinese adults with arthritis, exhibiting a nonlinear dose–response relationship with a pronounced threshold effect. TyGFI may serve as a practical, low-cost composite biomarker for stroke risk stratification in aging populations with chronic inflammatory conditions. </p>