Association between body roundness index and frailty among middle aged and older adults in China

Previous cross-sectional studies have indicated an association between the Body Roundness Index (BRI) and frailty. However, longitudinal evidence supporting this relationship remains scarce. Therefore, this study employs a longitudinal analysis to investigate the correlation between BRI and the risk of frailty in a Chinese population, and to evaluate the potential utility of BRI in the early identification and risk prediction of frailty. This study utilized data from the China Health and Retirement Longitudinal Study (CHARLS). A total of 4924 participants who completed follow-up from 2011 to 2018 were included. The BRI was calculated based on physical measurements and questionnaire data, and participants were categorized into quartiles according to BRI values. Multivariable-adjusted weighted regression models and trend tests were employed to examine the association between BRI and frailty. Furthermore, subgroup and sensitivity analyses were conducted to assess the robustness of the findings. After 7 years of follow-up, a total of 1242 participants (25.22%) developed frailty. The analysis revealed a positive association between the BRI and the risk of frailty (OR = 1.23, 95% CI: 1.15-1.33, p < 0.0001), with a significant increasing trend in frailty risk across ascending BRI quartiles (p for trend < 0.0001). Subgroup analyses and interaction tests indicated that the positive association between BRI and frailty risk remained consistent across various demographic, lifestyle, and clinical subpopulations (all p for interaction > 0.05). This study demonstrates that an elevated BRI is significantly associated with an increased risk of frailty. These findings suggest that while elevated BRI is an independent risk factor for frailty, its standalone predictive value is modest. It may serve as a supplementary indicator alongside other clinical assessments rather than an isolated diagnostic tool.