Association of triglyceride-glucose-related indices with adverse clinical outcomes in individuals with normal body mass index

Background and aims: The triglyceride-glucose (TyG) index serves as a reliable indicator of insulin resistance and metabolic risk factors. Most research has focused on obese individuals, with limited exploration in those with a normal body mass index (BMI). Method: This study analyzed 4,440 adults with normal BMI from NHANES 2003-2018. Logistic regression, linear regression, subgroup analysis, and survival analysis examined the relationship between TyG-related indices (TyG, TyG-BMI, TyG-WC, TyG-WHtR) and outcomes like liver fibrosis, stroke, cardiovascular disease (CVD), and mortality. Results: In 4,440 individuals, 279 developed CVD, 134 had stroke, 1,382 developed liver fibrosis, and 548 died, with a median observation period of 100 months (IQR, 59-145 months). The TyG index was divided into four quartiles (Q1, Q2, Q3, Q4) and significant trends in various clinical indicators across the quartiles were observed (demographic characteristics, metabolic and biochemical indicators). Further analysis revealed linear correlations between TyG, TyG-WC, TyG-BMI, TyG-WHtR and liver function metrics (ALT, AST, GGT, FIB-4, APRI), kidney function metrics (creatinine, eGFR, uric acid), and blood lipids (triglycerides, cholesterol) (P < 0.01). Univariate logistic regression showed that compared to Q1, Q4 showed a significantly higher risk of liver fibrosis, CVD, stroke, and death for all TyG-related parameters (P < 0.001). After adjusting for cofounders, TyG Q4 still had a significantly higher risk of liver fibrosis (P < 0.05) and mortality (P < 0.001); TyG-BMI Q4 showed a higher risk of mortality (P < 0.001); TyG-WC Q4 showed a significantly higher risk of liver fibrosis (P < 0.001), stroke (P < 0.01), CVD (P < 0.001), and mortality (P < 0.001); TyG-WHtR Q4 showed a significantly higher risk of liver fibrosis (P < 0.001), stroke (P < 0.01), CVD (P < 0.001), and mortality (P < 0.001). Subgroup analysis yielded similar conclusions. Additionally. Survival analysis revealed significant differences in survival across the different quartiles of TyG, TyG-WC, TyG-BMI, and TyG-WHtR (P < 0.001). Conclusion: The study identified a link between TyG-related markers and negative outcomes in individuals with a normal BMI, indicating that insulin resistance exists even in non-obese populations.