Background Despite BRI being a novel measure for chronic disease risk, the relationship between BRI and stroke risk under varying circadian syndrome (CircS) conditions is still unclear. Methods The analysis utilized data from 7535 participants involved in the China Health and Retirement Longitudinal Study (CHARLS). CircS was defined by at least four concurrent metabolic disturbances due to circadian rhythm disruption. To ensure robustness, the BRI‐stroke association was assessed using Cox models, restricted cubic splines, Kaplan–Meier curves, and mediation analyses, along with subgroup and sensitivity analyses. The receiver operating characteristic (ROC) analysis was used to compare the stroke risk prediction performance of BRI with conventional metabolic indices. Results Following full adjustment, higher log (BRI) values were significantly associated with an increased risk of stroke (HR = 2.50, 95% CI: 1.81–3.44, p 0.05). However, the association remained significant in non‐CircS individuals (log (BRI) HR = 2.36, 95% CI: 1.61–3.47; Q4 vs. Q1 HR = 2.08, 95% CI: 1.46–2.98; all p < 0.001). Subgroup and sensitivity analyses bolstered the robustness of our findings. CircS mediated 21.0% of the association between BRI and stroke risk (95% CI: 18%–91%, p < 0.001). With an area under the curve (AUC) of 0.656, BRI demonstrated moderate predictive capability for stroke, outperforming other anthropometric indices. Conclusions An increased BRI is associated with a higher stroke risk, partially mediated by CircS, highlighting the potential role of circadian health in stroke prevention.
Ma et al. (2026) studied this question.