The association of triglyceride-glucose index and related indices with all-cause and cardiovascular mortality in biologically aging populations

The relationship between the triglyceride-glucose index (TyG) and all-cause and cardiovascular mortality in biological aging (BA) populations remains unclear. This study aimed to investigate the role of TyG and its derived indices (TyG-Body Mass Index [TyG-BMI] and TyG-Waist-to-Height Ratio [TyG-WHtR]) as potential biomarkers of mortality risk in biologically aging populations. This study included participants from the National Health and Nutrition Examination Survey database between 1999 and 2018 and constructed 3 metabolism-related indices: TyG, TyG-BMI, and TyG-WHtR. Kaplan-Meier survival curves, Cox regression analysis, trend tests, and restricted cubic splines were used to assess the relationship between TyG-related indices and all-cause and cardiovascular mortality in BA populations (including Klemera-Doubal biological age acceleration [KDM-BA] and phenotypic age acceleration [PA]). Subgroup and interaction analyses were performed. Survival analysis showed that, in the KDM-BA population, higher quartiles of TyG, TyG-BMI, and TyG-WHtR were significantly associated with worse survival outcomes. In the PA population, higher TyG and TyG-WHtR levels also indicated worse survival (P < .001 for both), but no significant difference was found for TyG-BMI in all-cause mortality (P = .313). Fully adjusted Cox regression analysis further confirmed that in the KDM-BA population, TyG and its related indices were significantly associated with both all-cause and cardiovascular mortality hazard ratio (HR range: 1.19-1.34, P < .05). In the PA population, TyG was significantly associated with both types of mortality (HR range: 1.16-1.19, P < .05), whereas TyG-WHtR was only associated with cardiovascular mortality (HR = 1.26, P = .022). TyG-BMI was not significantly associated with either type of mortality. Nonlinear analysis revealed a significant dose-response relationship between TyG and mortality in both populations, with the mortality risk significantly increasing above a certain threshold (approximately 8.1). In the PA population, TyG-BMI and TyG-WHtR showed significant nonlinear relationships with all-cause mortality. Specifically, when TyG-BMI exceeded 215.145, the risk of death increased significantly (HR = 1.00, P = .031, nonlinear P < .001), and when TyG-WHtR exceeded 5.034, the risk of death also increased significantly (HR = 1.20, P < .001, nonlinear P = .004). Subgroup analysis showed that the association between TyG and its related indices and mortality risk was stronger in individuals aged < 65 years and those with higher BA (e.g., KDM-BA and PA ≥ 5). Medication use had a limited effect on these associations, with only minor enhancements observed in some subgroups. This study underscores the significance of TyG and its related indices (TyG-BMI and TyG-WHtR) as key indicators of all-cause and cardiovascular mortality in biologically aging populations. Notably, strong associations were found in the KDM-BA cohort, particularly among individuals aged < 65 years and those with advanced BA. These findings suggest that TyG and its related indices may play a crucial role in the long-term management of biologically aging populations and serve as valuable biomarkers for identifying high-risk individuals. This further highlights the importance of metabolic dysregulation in the aging process and its contribution to an increased mortality risk.