Longitudinal trajectories of the C-reactive protein-triglyceride-glucose index and frailty progression in two nationwide prospective cohorts.

<h4>Background</h4>The C-reactive protein-triglyceride-glucose index is a novel biomarker reflecting combined cardiometabolic and inflammatory burdens. This dual-cohort study investigated relationships between longitudinal trajectories of this index and multidimensional frailty progression.<h4>Methods</h4>We analyzed data from the China Health and Retirement Longitudinal Study and the English Longitudinal Study of Aging. K-means clustering partitioned continuous longitudinal index measurements into distinct developmental trajectories. Frailty was evaluated using a 31-item index. After adjusting for covariates, multivariable linear regression, Cox proportional hazards, and linear mixed-effects models evaluated cross-sectional associations, incident risk, and dynamic accumulation velocity of frailty, respectively.<h4>Results</h4>The analysis included 3947 Chinese and 1431 English participants. Clustering identified consistently low, moderate, and high trajectories. Compared with the low trajectory, the high group exhibited a more severe baseline frailty score (Chinese cohort: β = 1.96, 95% confidence interval 1.03-2.91; English cohort: β = 2.42, 95% confidence interval 1.04-3.80). During follow-up, the high trajectory was independently associated with augmented incident frailty risk (Chinese cohort: hazard ratio 1.24, 95% confidence interval 1.03-1.49; English cohort: hazard ratio 1.42, 95% confidence interval 1.06-1.90). Furthermore, linear mixed-effects modeling revealed accelerated deficit accumulation over time in this high-risk group (Chinese cohort: β = 0.263, 95% confidence interval 0.074-0.451; English cohort: β = 0.330, 95% confidence interval 0.214-0.445). These effects remained robust across body mass index classifications.<h4>Conclusions</h4>Consistently high longitudinal trajectories of the C-reactive protein-triglyceride-glucose index serve as powerful, dynamic indicators of incident frailty and accelerated biological aging. Tracking this cumulative metabolic and inflammatory burden provides an accessible clinical strategy for early risk identification.