Prognostic associations of anthropometric indices with major health outcomes: A nationwide cohort study of 1.1 million adults.

BACKGROUND AND AIMS: The global escalation of obesity necessitates precise tools for assessing diverse health risks. This study aimed to compare the prognostic associations of body mass index (BMI), waist circumference (WC), and the body roundness index (BRI) across multiple cardiovascular and mortality outcomes in a large cohort of Korean adults using a nationwide database. METHODS: This retrospective cohort study analyzed 1,199,633 Korean adults (aged ≥55 years) from the National Health Insurance Service database. Prognostic association for atherosclerotic cardiovascular disease (ASCVD), all-cause mortality, and atrial fibrillation (AF) over a 10-year follow-up was assessed using receiver operating characteristic (ROC) analysis and multivariable Cox proportional hazards models. RESULTS: No single index consistently outperformed the others; rather, association was outcome-specific. BRI demonstrated the highest discrimination for ASCVD (AUC: 0.553) compared to WC (0.540) and BMI (0.512; P < 0.05 for all). Conversely, BMI showed the highest AUC for all-cause mortality (0.595), largely due to a significant inverse relationship in the underweight category. For incident AF, WC showed the highest AUC (0.567), followed by BRI (0.550) and BMI (0.527). Restricted cubic spline analyses revealed non-linear (U-shaped or J-shaped) relationships for most outcomes. CONCLUSIONS: These findings indicate that each anthropometric index captures distinct biological aspects of adiposity, highlighting the need to consider the specific clinical outcome when interpreting obesity-related risk.