Triglyceride-glucose index in non-obese individuals: its association with and predictive value for non-alcoholic fatty liver disease

Abstract

To investigate the association of triglyceride-glucose index (TyG) with non-alcoholic fatty liver disease (NAFLD) and its diagnostic value for NAFLD in non-obese individuals. We retrospectively collected the data of non-obese individuals (BMI < 25 kg/m2) undergoing routine health examination at Second Affiliated Hospital of Xi'an Jiaotong University between May, 2020 and December, 2023, who all received abdominal ultrasound examination for NAFLD screening. The nonlinear relationship between TyG and non-obese NAFLD was explored using restricted cubic splines (RCS), and LASSO regression was used for variable screening; the correlation between TyG and NAFLD risk was analyzed using multivariate logistic regression. The diagnostic value of TyG for non-obese NAFLD was assessed using receiver-operating characteristic (ROC) curves and sensitivity analysis. A total of 3723 non-obese subjects were enrolled in this study, including 432 (11.6%) patients with NAFLD. Compared with the healthy individuals, the patients with NAFLD had significant elevations of systolic and diastolic blood pressures, total cholesterol, triglycerides, LDL-C, blood uric acid, fasting blood glucose, and TyG index and a decreased HDL-C level (P < 0.05). Multivariate logistic regression revealed that for each one-unit increase of TyG, the risk of non-obese NAFLD increased by 2.2 folds (OR=3.22, 95% CI: 2.53-4.12, P < 0.001). Compared with a TyG index in the lowest quartile Q1, a TyG index in the Q2, Q3 and Q4 quartiles was associated with an increased risk of NAFLD by 1.52 folds (OR=2.52, 95% CI: 1.20-5.95), 3.56 folds (OR=4.56, 95% CI: 2.28-10.46), and 8.66-folds (OR=9.66, 95% CI: 4.83-22.18), respectively. The RCS curve demonstrated a significant linear correlation between TyG index and non-obese NALFD risk (P for nonlinear= 0.019). For diagnosing non-obese NALFD, TyG index had an area under ROC curve of 0.819 with a sensitivity of 78.0% and a specificity of 71.2%. An increase of TyG index is correlated with increased risks of NAFLD in non-obese individuals and can serve as an indicator for screening early NAFLD in healthy individuals.