The body roundness index (BRI) is a more comprehensive anthropometric measure than the body mass index (BMI) because it reflects the distribution of visceral fat more accurately. This study evaluated the separate and joint associations of cumulative BRI (cumBRI) exposure and its variability with the risk of fragility fractures in the Chinese population. This study included 47,240 individuals from the Kailuan Study who underwent three consecutive health examinations between 2006 and 2010 (2006–2007, 2008–2009, and 2010–2011) and were followed up until December 31, 2022. Cumulative BRI exposure was calculated using the time-weighted average (TWA), and variability in BRI was assessed using indices of variability. Cox models were used to estimate the hazard ratios (HRs) and 95% confidence intervals (CIs). Subgroup analysis and interaction testing performed. The C-index, discriminatory improvement (IDI), and net reclassification index (NRI) were used to assess fracture risk prediction. During a median follow-up of 12.03 years, 725 participants developed fragility fractures. After adjusting for confounders, the HR for fragility fracture was 1.52 (95% CI 1.15–1.99) in the highest TWA BRI quartile, 1.38 (95% CI 1.08–1.75) in those with a cumulative burden of > 0, and 1.55 (95% CI 1.20-2.00) for those with ≥ 4 years of exposure duration. Greater BRI variability was associated with an increased risk of fragility fractures (HR 1.29, 95% CI 1.05–1.60]). The risk of fragility fractures was higher in individuals with a high TWA BRI and high BRI variability than in those with a low TWA BRI and low BRI variability. Combined measures of cumulative BRI and variability were better able to predict the risk of fracture than traditional metrics. Cumulative exposure to a high cumBRI and greater BRI variability in the BRI were independently associated with a higher incidence of fragility fractures, and their coexistence could may further increase the risk further. In terms of predicting the fracture risk, the combined effects of cumulative cumBRI exposure and variability predicting fracture risk are slightly superior to the predictive ability of obesity-related indices.
Yang et al. (Tue,) studied this question.