Joint association of triglyceride glucose index (TyG) and body roundness index (BRI) with stroke incidence: a national cohort study

Abstract Background Insulin resistance (IR), as quantified by the triglyceride glucose (TyG) index, and visceral obesity, as assessed by the body roundness index (BRI), have been identified as pivotal risk factors for stroke. However, the combined impact of these two indicators on stroke risk has not been thoroughly investigated. This study aims to investigate both the separate and combined associations, as well as potential interactions, between the TyG index and/or BRI with respect to stroke incidence. Methods This cohort study encompassed 6621 respondents who were free of stroke at baseline from the China Health and Retirement Longitudinal Study (CHARLS). Participants were categorized based on the median values of the TyG index or/and BRI. Cox proportional hazards regression models were employed to examine the associations between the TyG index alone, BRI alone, and their combined effects on stroke incidence. Both additive and multiplicative interaction effects were further estimated. Results Among 6621 participants aged 45 years or older, the mean (SD) age was 58.06 (8.57) years, with 2951 (44.6%) being male. During a follow-up period of up to 9 years, 743 individuals experienced stroke events. Compared to participants with low TyG index and low BRI, the adjusted hazard ratios (HRs) were as follows: 1.36 (95% confidence interval [CI] 1.05–1.75) for high TyG index alone, 1.61 (95% CI 1.27–2.05) for high BRI alone, and 1.78 (95% CI 1.40–2.26) for high TyG index and high BRI. Neither additive nor multiplicative interactions between BRI and TyG for incident stroke were statistically significant. The combination of TyG and BRI enhanced the predictive capability for stroke compared to either biomarker alone. Conclusion We discovered that both the TyG index and BRI are strongly associated with stroke incidence. The joint assessment of TyG and BRI enhances the predictive capability for stroke, underscoring the critical role of IR and visceral adiposity in the identification and screening of stroke risk. Graphical abstract