Age-Related Trajectories of the Triglyceride–Glucose Index and All-Cause Mortality in Older Chinese Adults

Background: The triglyceride–glucose (TyG) index is recognized as an alternative biomarker of cardiometabolic health, associated with insulin resistance and the development and prognosis of cardiovascular disease (CVD). However, the prospective association between long-term TyG index trajectories and all-cause mortality in the older population remains incompletely elucidated. Methods: This longitudinal retrospective cohort study included 93,418 older adults who underwent repeated general health assessments at The Third Xiangya Hospital of Central South University between 2012 and 2020. The TyG index was calculated utilizing the formula: ln (fasting triglycerides (mg/dL) × fasting glucose (mg/dL)/2). TyG index trajectories during the follow-up were analyzed using latent class trajectory modeling (LCTM). Baseline TyG index values and TyG trajectories were analyzed using a Cox proportional hazards model to estimate hazard ratios (HRs) and 95% confidence intervals (CIs). Results: Over a median follow-up of 5.4 years, 7364 participants died, including 4176 cardiovascular deaths. Each 1-standard deviation (SD) increase in the TyG index was associated with a 18.9% higher risk of all-cause mortality, even after accounting for traditional CVD risk factors (HR 1.189, 95% CI 1.144–1.235). Similar associations were observed when the TyG index was modeled in quartiles. Based on the observed trajectory patterns, participants were classified into four groups: low, moderate–low, moderate, and high TyG index trajectories. The low, moderate–low, and high trajectory groups were independently associated with all-cause mortality, whereas the moderate group was not. Following multivariable adjustment, the moderate–low group exhibited a 1.104-fold increase in all-cause mortality risk (95% CI: 1.047–1.165), whereas the high group demonstrated a 1.243-fold increase (95% CI: 1.139–1.357), with both findings statistically significant (p < 0.001). Meanwhile, no significant association was found between the low group and the study outcomes (HR 0.998, 95% CI 0.875–1.138; p = 0.972). Conclusions: In this large cohort of older adults, moderate-low and high TyG index trajectories were associated with an increased risk of all-cause mortality. Longitudinal patterns of the TyG index may serve as important indicators for identifying individuals at elevated risk of all-cause mortality and may support the development of targeted preventive and therapeutic interventions.