Association between body roundness index and stroke incidence among middle-aged and older adults in China: a longitudinal analysis of the CHARLS data.

To evaluate the association between body roundness index (BRI) and stroke risk in middle-aged and elderly Chinese population. This retrospective cohort study utilized data from the China Health and Retirement Longitudinal Study (CHARLS), including participants aged ≥45 years. BRI was the exposure variable, and stroke incidence was the outcome. Weighted Cox regression models analyzed the association and evaluated the threshold effect of BRI on stroke risk. Among 7651 participants, 519 stroke cases were identified. A one-unit increase in BRI was associated with a 15.8% elevated stroke risk [hazard ratio (HR) = 1.158, 95% confidence interval (CI): 1.158-1.159, P < 0.00001]. Quartile analysis revealed that the highest BRI quartile group had an 80.3% increased stroke risk compared to the lowest quartile (HR = 1.803, 95%CI: 1.800-1.806, P < 0.00001). A threshold effect was observed: when BRI was <5.94, a 1-unit increase was associated with an 18% increased stroke risk (HR = 1.18, 95%CI: 1.08-1.29, P = 0.0002). However, when BRI was >5.94, a 1-unit increase was associated with a non-significant 13% decreased risk (HR = 0.87, 95%CI: 0.68-1.12, P = 0.2944). BRI is significantly and positively associated with stroke risk in middle-aged and elderly Chinese population, with a threshold effect observed. BRI may serve as a valuable marker for stroke prediction and prevention, particularly at lower levels. Further research is needed to investigate BRI's applicability in diverse populations and its potential in developing stroke prevention strategies. Key message What is already known on this topic. Stroke remains a leading cause of death and disability, particularly in China, emerging body shape indices warrant investigation as cardiovascular predictors, extending beyond the cross-sectional associations documented in previous studies. What this study adds. In this first longitudinal study of Chinese adults aged 45 and older, we identified four distinct BRI trajectory patterns over a 10-year follow-up, revealing that consistently high and rapidly increasing trajectories were associated with elevated stroke risk, with notable gender differences. How this study might affect research, practice, or policy. Our findings support BRI trajectory monitoring as a valuable stroke risk assessment tool, emphasizing the importance of gender-specific prevention strategies, stable body shape maintenance, and early intervention for unfavorable patterns.