Body roundness index and all-cause and CVD mortality: findings from Japanese adults and meta-analysis

Background: Although body roundness index (BRI) is gaining attention as an indicator of abdominal obesity, evidence on this indicator is still sparse. We aimed to summarize basic information about BRI in a Japanese population and to examine associations of BRI with all-cause and cardiovascular disease (CVD) mortality with a meta-analysis. Methods: This population-based cohort study included participants (mean age of 58.4 years, 37.8% men) in health check-up programs between 2004 and 2018, and we followed up until December 31, 2023. BRI was calculated by a conventional formula for height (cm) and waist circumference (cm). Mortality was ascertained by death certifications. CVD mortality was defined as mortality with ICD-10 codes of I00-I99. Hazard ratios were estimated for all-cause and CVD mortality using Cox proportional hazards regression models. Results: During the follow-up period (median: 13.3 years), 206 individuals died, and 47 individuals died by CVD. Women had a wider distribution of BRI (median: 3.72; IQR: 2.84, 4.88) compared with men (median: 3.54; IQR: 2.88, 4.19). BRI increased from the 40-49 age group (median: 3.24; IQR: 2.42, 4.08) to those over 70 years old (median: 4.22; IQR: 3.20, 5.32). Compared with Q1, HRs (95% CI) in Q3 were lower for both all-cause mortality (HR: 0.64, 95% CI: 0.43, 0.96) and CVD mortality (HR: 0.27, 95% CI: 0.09, 0.78). Meta-analysis also showed similar associations. Conclusions: BRI varies across age groups and between sexes in a Japanese population. Both our results and this meta-analysis suggest that BRI has U-shaped associations with all-cause and CVD mortality.