Nonlinear association between body roundness index and metabolic dysfunction associated steatotic liver disease in nondiabetic Japanese adults.

The global rise in obesity and diabetes has been paralleled by a rising incidence of metabolic dysfunction-associated steatotic liver disease (MASLD). Although previous studies have explored the association between body roundness index (BRI) and MASLD, the specific relationship in non-diabetic Japanese adults requires further investigation. This study analyzed data from 15,299 participants enrolled in the NAGALA cohort (2004-2015) to explore the association between BRI and MASLD through multivariable logistic regression, stratified analysis, and restricted cubic spline modeling. The prevalence of MASLD was 14.46%, with 13.73% occurring in non-obese individuals (BMI < 30). After adjusting for all confounding factors, BRI demonstrated a significant association with MASLD, yielding an adjusted odds ratio of 1.72 (95% CI 1.48-1.99). The restricted cubic spline model revealed a nonlinear relationship, with an inflection point at 3.06. Stratified analyses revealed stronger associations in individuals with lower BMI (≤ 24 kg/m).