Central Adiposity Assessed with Body Roundness Index and Mortality: The Seguimiento Universidad de Navarra...

Background/Objectives: Obesity is currently a global pandemic and a major risk factor for the development of chronic disease and increased mortality. Common methods used to define obesity, such as body mass index (BMI), do not accurately reflect body fat content or distribution. Methods: We investigated the prognostic significance of the body roundness index (BRI) on incident death in 12,642 participants (60.2% women, mean age: 39, standard deviation (SD): 12 years) from the "Seguimiento Universidad de Navarra" prospective cohort and compared it to waist-to-height ratio (WtHR) and waist circumference (WC). Participants were monitored through biennial questionnaires. The mean of the baseline BRI was 3.6 (SD: 1.4) units. Multivariable-adjusted Cox models were used to estimate hazard ratios (HR) and confidence intervals (CI) of death. Results: Over a median follow-up period of 11.5 years, 380 participants died (absolute mortality rate 1.74 × 10^-3). In multivariable-adjusted models, higher quartiles of BRI were significantly associated with all-cause death, specifically in those ≥ 60 years (Quartile 4 vs. Quartile 1: HR 1.64; 95% CI: 1.00, 2.70). Considering the whole group (all ages), each 2-unit increase in BRI was linked to a 21% higher all-cause mortality risk in both men and women. This association was even stronger for participants aged over 60 years (multivariate adjusted HR for 2-unit BRI increase: 1.31; CI: 1.00, 1.72), while it was not significant when considering only those under 60 years. The associations of z-WtHR and z-WC with incident mortality for all participants were also significant in the fully adjusted model (HRs: 1.14; CI: 1.01, 1.27, and HRs: 1.16; CI: 1.04, 1.30, respectively). Mortality associations assessed using the BRI, WtHR, and WC were superior to associations based on the BMI. Conclusions: BRI shows a linear link with all-cause mortality in healthy adults ≥ 60, while WtHR and WC were also mortality predictors. Thus, lower central fat may help reduce early death risk.