Differential predictive ability of the novel obesity indices on hypertension among non-obese adults stratified by metabolic health

Background: Novel obesity indices that integrate visceral adiposity, insulin resistance, and lipid metabolism may predict hypertension (HTN) better than conventional anthropometric measures. We compared novel and traditional obesity indices for HTN among non-obese Mongolian adults according to metabolic health status. Methods: We used data from the 2019 Mongolian WHO STEPwise survey (STEPS) and included adults aged 18-65 years with a body mass index (BMI) <30 kg/m2. Exposures were triglyceride- and triglyceride-glucose (TyG)-derived indices, including the TyG-waist-to-height ratio (TyG-WHtR), and traditional anthropometric indices; the outcome was HTN. Participants with diabetes or dyslipidemia were classified as metabolically unhealthy (MUI) and the remainder as metabolically healthy (MHI). Multivariable logistic regression and receiver operating characteristic (ROC) analyses were performed. Results: Of 3,031 participants, 61.4% had HTN, and the mean age was 40.9 (SD 11.5) years. TyG-WHtR had the largest odds ratio (OR) for HTN in both MHI (OR 1.68, 95% CI 1.43-1.97) and MUI (OR 1.72, 95% CI 1.46-2.04), followed by the body roundness index (BRI). Indices based mainly on lipids and glucose were not positively associated with HTN. Discrimination was modest; the highest areas under the curve (AUC) were for BMI (0.657) among MHI and for BRI and WHtR (0.691) among MUI. Conclusions: Among non-obese adults, anthropometric and TyG-anthropometric indices, particularly TyG-WHtR, were associated with HTN regardless of metabolic status, whereas lipid-only indices were not. Discrimination was modest and greater in MUI, and simple measures such as BMI and waist circumference performed as well as the novel indices.