Body Roundness Index and All-Cause and Cardiovascular Mortality: Findings from Japanese Adults and Preliminary Meta-analysis

Background: Although body roundness index (BRI) is gaining attention as an indicator of abdominal obesity, evidence on this indicator is still sparse. Objectives: 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 preliminary meta-analysis. Methods: This population-based cohort study included participants [mean age of 58.4 y (min, max: 40, 89), 37.8% men] in health check-up programs between 2004 and 2018, and we followed up until 31 December, 2023. BRI was calculated by a conventional formula for height (cm) and waist circumference (cm). CVD mortality was defined as mortality with International Classification of Diseases, 10th Revision codes of I00–I99. Hazard ratios (HRs) were estimated for all-cause and CVD mortality using Cox proportional hazards regression models. Results: During the follow-up period (median: 13.3 y), 206 individuals died, and 47 individuals died from CVD. Women had a wider distribution of BRI [median: 3.72; interquartile range (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 y old (median: 4.22; IQR: 3.20–5.32). Compared with Q1, HRs [95% confidence interval (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). Preliminary meta-analysis also supported a similar U-shaped association of BRI with mortality with a HR in Q3 of 0.85 (95% CI: 0.75, 0.95) compared with Q1. 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. The trial was registered at PROSPERO as 1149845.