Association of the triglyceride–glucose index with all-cause and cardiovascular mortality among individuals with cardiovascular–kidney–metabolic syndrome: a population-based cohort study using data from the US National Health and Nutrition Examination Survey, 1999–2018

Objective The study investigated the association between the triglyceride–glucose (TyG) index (a surrogate measure for insulin resistance) and all-cause and cardiovascular disease (CVD) mortality among individuals with cardiovascular–kidney–metabolic syndrome. Design Population-based cohort study. Setting US National Health and Nutrition Examination Survey, 1999–2018. Participants A total of 13 585 participants who had valid data were included in this analysis. Outcome measures Data from the participants were linked to death certificates to obtain follow-up mortality information from the National Death Index. Cox proportional hazards models were used to assess the associations between the TyG index and all-cause and CVD mortality. Non-linear associations and threshold effects were investigated using restricted cubic spline regression and a two-piecewise Cox proportional hazards model. Results During a median follow-up of 99 months, a total of 2876 (16.24%) deaths occurred, of which 961 were attributed to CVD. Each one-unit increase in the TyG index was associated with an 8.9% relative increase in the hazard of all-cause mortality (HR 1.089, 95% CI 1.013 to 1.171) and a 19.5% relative increase in the hazard of CVD mortality (HR 1.195, 95% CI 1.027 to 1.390). Non-linear relationships were identified between the TyG index and all-cause and CVD mortality, with threshold values of 8.97 and 8.81 for all-cause and CVD mortality, respectively. A significant interaction effect was found between age and the TyG index. Conclusion There was a U-shaped relationship between the TyG index and both all-cause and CVD mortality. The thresholds of the TyG index may serve as potential tools for managing populations with cardiovascular–kidney–metabolic syndrome to reduce mortality risk.