Associations of the triglyceride-glucose index with mortality mediated by blood urea nitrogen among critically ill patients: a cohort study

Previous studies have shown that an elevated triglyceride-glucose (TyG) index is associated with all-cause mortality in patients. However, the potential mediating effect of blood urea nitrogen (BUN) within these associations has not been reported. The focus of this study was to investigate the potential mediating effect of BUN within these associations. This was a retrospective cohort study of patients in the eICU Collaborative Research Database (eICU-CRD) from 208 different ICUs in the United States between 2014 and 2015 that explored. The primary endpoint of the study was all-cause mortality within 28 days of ICU admission. In addition, the following formula was used to calculate the TyG index: Ln [fasting TG (mg/dL) × FBG (mg/dL)/2]. Cox regression model and subgroup analysis were performed to assess the associations of TyG index with 28-day mortality. The mediating effect of BUN was assessed to investigate the potential mechanism of the associations between TyG index and mortality using the mediation package in R 4.2.0. Of the 14,414 patients with a mean age of 64.1 years, 809 (5.61%) died within 28 days of ICU admission. The proportion of women was 57.9% and the mean TyG index was 8.97 ± 0.82. In the multivariable-adjusted model, the high tertile showed an even stronger association with 28-day ICU mortality than the low tertile, with a hazard ratio (HR) of 1.27 (95% CI: 1.05, 1.53; P = 0.014). Mediation analysis showed that BUN mediated 12.4% of the association between the TyG index and mortality. Our study showed that an elevated TyG index was associated with an increased risk of mortality in critically ill patients. The association appeared to be partially mediated by BUN.