The triglyceride-glucose index is a predictor for cardiovascular and all-cause mortality in CVD patients with diabetes or pre-diabetes: evidence from NHANES 2001–2018

BACKGROUND: The association between the triglyceride-glucose (TyG) index and mortality in cardiovascular disease (CVD) patients with diabetes or pre-diabetes remains unclear. This study aimed to investigate the relationship between baseline TyG index and all-cause and cardiovascular (CV) mortality in CVD patients with diabetes or pre-diabetes among American adults. . METHODS: This study enrolled 1072 CVD patients with diabetes or pre-diabetes from the National Health and Nutrition Examination Survey (2001–2018). Mortality outcomes were determined by linking to National Death Index (NDI) records up to December 31, 2019. Multivariate Cox proportional hazards models were constructed to analyze explore the associations between baseline TyG index and mortality. Non-linear correlations were explored using restricted cubic splines, and a two-piecewise Cox proportional hazards model for both sides of the inflection point was constructed. RESULTS: During 7541 person-years of follow-up, a total of 461 all-cause deaths and 154 CVD-related deaths were recorded. The restricted cubic splines revealed a U-shaped association between the baseline TyG index with all-cause and CVD mortality in CVD patients with diabetes or pre-diabetes. Specifically, baseline TyG index lower than the threshold values (TyG index < 9.05 in all-cause mortality and < 8.84 in CVD mortality) was negatively associated with mortality (HR 0.47, 95% CI = 0.27–0.81 for all-cause mortality and HR 0.25, 95% CI = 0.07–0.89 for CVD mortality). In contrast, baseline TyG index higher than the threshold values (TyG index > 9.05 in all-cause mortality and > 8.84 in CVD mortality) was positively associated with mortality (HR 1.42, 95% CI = 1.02–1.99 for all-cause mortality and HR 1.77, 95% CI = 1.08–2.91 for CVD mortality). CONCLUSIONS: A U-shaped association was observed between the baseline TyG index with CVD and all-cause mortality in CVD patients with diabetes or pre-diabetes in a American population. The thresholds of 8.84 and 9.05 for CVD and all-cause mortality, respectively.