Body Roundness Index and Body Shape Index as Predictors for All-Cause Mortality Beyond Body Mass Index: Findings From...

Body mass index (BMI) has been criticised for its inability to differentiate between fat and nonfat tissues and to reflect body fat distribution. Body Roundness Index (BRI) and A Body Shape Index (ABSI) are novel indices addressing these limitations, yet their mortality risk-stratification utility remains understudied in Asian populations.

In this retrospective cohort study using a nationally representative Japanese claims database (2014-2022), we analysed 778,812 individuals who underwent healthcare checkups. Anthropometric indices were categorised into five groups based on restricted cubic spline curve-derived cutoffs. Multivariate Cox proportional hazards models, adjusted for demographic factors, lifestyle variables and comorbidities, assessed associations between these categorical variables and all-cause mortality.

Among participants (mean [standard deviation] age of 62.8 [9.6] years and 445,250 [57.2%] women), 14,690 deaths occurred during a median [interquartile range] follow-up of 4.53 [3.28-6.23] years. While BMI and BRI showed U-shaped relationships with all-cause mortality, ABSI demonstrated a J-shaped relationship. Significant differences in mortality risk compared with the reference category were observed in three categories for BMI, four categories for BRI and four categories for ABSI.

BRI and ABSI identified mortality risk differences across more categories than BMI, indicating that these indices may provide additional insights beyond BMI for mortality risk assessment.