Association of triglyceride-glucose index with all-cause and non-cardiovascular mortality in patients with obstructive sleep apnea: an age-stratified analysis

BACKGROUND: The predictive value of the triglyceride-glucose (TyG) index in patients with obstructive sleep apnea (OSA) remains unclear. Therefore, we aimed to investigate the associations between the TyG index and all-cause and non-cardiovascular (non-CV) mortality in an OSA cohort, focusing on age differences. METHODS: This study enrolled 10,274 patients with OSA from the National Health and Nutrition Examination Survey (2005-2008 and 2015-2018). Mortality outcomes were ascertained by linking to National Death Index records through December 31, 2019. Multivariate Cox proportional hazards regression models with restricted cubic splines and interaction tests with age were employed to evaluate the association between the TyG index and all-cause and non-CV mortality. Kaplan-Meier analysis was used to evaluate mortality differences. RESULTS: During a mean follow-up of 88 months, 1027 all-cause deaths occurred, of which non-CV deaths accounted for 77.8% of the total mortality burden. After fully adjusting for potential confounders, our study explored a U-shaped association between the TyG index and all-cause/non-CV mortality (both non-linear p < 0.001), with inflection points at 9.27 and 9.2. Age yielded a statistically significant interaction between the TyG index and mortality. The TyG index was linearly associated with higher risks of all-cause [Hazard Ratio (HR) 1.30, 95% Confidence Interval (CI): 1.09-1.55, p = 0.004] and non-CV mortality (HR 1.33, 95% CI: 1.08-1.62, p = 0.006) in participants aged < 65, but not in participants age ≥ 65. Kaplan-Meier curves indicated that the patients with the higher TyG index had a significantly lower survival probability (All-cause mortality: p for log-rank test < 0.001; non-CV mortality: p for log-rank test = 0.001). CONCLUSIONS: This study identified a U-shaped association between the TyG index and all-cause and non-CV mortality in an OSA population, with a statistically significant interaction with age. A linear relationship was detected between the TyG index and mortality in those aged < 65, while a non-linear association was established in those aged ≥ 65.