What question did this study set out to answer?

This research aims to investigate how cumulative body roundness index (BRI) and its variability relate to fragility fracture risk.

March 13, 2026Open Access

Independent and synergistic associations of cumulative body roundness index and its variability with fragility fracture risk

Key Points

This research aims to investigate how cumulative body roundness index (BRI) and its variability relate to fragility fracture risk.
Included 47,240 individuals from the Kailuan Study with three health examinations from 2006 to 2010.
Calculated cumulative body roundness index exposure using time-weighted averages.
Assessed BRI variability using indices of variability and applied Cox models for risk estimation.
Performed subgroup analysis and interaction testing to evaluate fracture risk.
Utilized C-index, IDI, and NRI to assess the predictive power for fracture risk.
During 12.03 years of follow-up, 725 participants suffered fragility fractures.
Hazard ratio for the highest quartile of TWA BRI was 1.52, indicating increased risk.
Each one-unit increase in BRI variability correlated with a hazard ratio of 1.29 for fractures.
Higher cancer risk was noted in individuals with both high TWA BRI and variability compared to those with low levels.
Combined measures of cumBRI and variability improved fracture risk prediction beyond traditional obesity metrics.

Abstract

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.

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