Abstract
BACKGROUND: Frailty is notably prevalent in individuals aged 50 and older and has been associated with metabolic dysfunction. The triglyceride-glucose (TyG) index is a reliable surrogate marker for insulin resistance. This study aimed to investigate the association between the TyG index and frailty in middle-aged and older Chinese adults. METHODS: This study used 7-year data from wave 1 (2011) to wave 4 (2018) in the China Health and Retirement Longitudinal Study. Using the Rockwood frailty index (FI), participants were categorized as non-frail (FI < 0.25) or frail (FI ≥ 0.25). The TyG index was calculated as ln [fasting triglyceride (mg/dL) × fasting plasma glucose (mg/dL)/2]. TyG trajectories were analyzed using data in wave 1 and wave 3 (2015). Associations were assessed using logistic and Cox regression models. RESULTS: At baseline in 2011, among 6,003 participants (median age, 60 years; 51.2% men), there were 684 cases of prevalent frailty. Cross-sectionally, the TyG index was not associated with frailty. In the prospective analysis of 3957 participants (median age, 60 years; 51.8% men), 1427 developed new-onset frailty during the 7-year follow-up. Compared with participants in the lowest tertile (T1), those in TyG index tertiles 2 and 3 had a 1.16-fold (hazard ratio [HR], 1.16; 95% CI 1.02-1.33; P = 0.03) and 1.19-fold (HR, 1.19; 95% CI 1.03-1.39; P = 0.02) higher risk of new-onset frailty, respectively. Each 1-unit increase in the TyG index was associated with an 18% increase in the risk of new-onset frailty (HR, 1.18; 95% CI 1.08-1.30; P < 0.01). Trajectory analysis identified three longitudinal patterns of the TyG index: "stable" (n = 3505, 87.2%), "increase" (n = 413, 10.3%), and "rapid decrease" (n = 100, 2.5%). After adjusting for covariates, participants in the "increase" trajectory had a significantly higher risk of frailty (HR, 1.30; 95%CI 1.01-1.69; P < 0.05) compared with those in the "stable" trajectory. CONCLUSIONS: Elevated metabolic risk, as evaluated by the TyG index, was prospectively associated with an increased risk of frailty in middle-aged and older adults, although cross-sectional analysis was negative. These results suggest that the TyG index may serve as a valuable biological marker for identifying individuals at risk of future frailty.