Systolic blood pressure status modifies the associations between the triglyceride-glucose index and incident cardiovascular disease: a national cohort study in China

Abstract Background The triglyceride-glucose (TyG) index and blood pressure (BP) are correlated and serve as risk factors for cardiovascular disease (CVD). The potential impact of BP status on the association between the TyG index and CVD risk remains uncertain. This study aims to investigate the relationships between the TyG index and incident CVD in Chinese middle-aged and elderly adults, considering variations in BP status among participants. Methods 6558 participants (mean age: 58.3 (± 8.7) years; 46.0% were men) without prevalent CVD were recruited from the China Health and Retirement Longitudinal Study. Participants were divided into three groups according to their systolic blood pressure (SBP) levels (< 120mmHg, 120 ∼ 129mmHg, ≥ 130mmHg). The TyG index was computed as ln[triglyceride (mg/dl) * fasting blood glucose (mg/dl)/2]. The primary outcome was CVD (heart disease and stroke), and the secondary outcomes were individual CVD components. Cox regression models and restricted cubic splines were performed to investigate the associations between continuous and categorical TyG with CVD. Results 1599 cases of CVD were captured during 58,333 person-years of follow-up. Per 1-SD higher TyG index was associated with a 19% (HR: 1.19; 95% CI: 1.12, 1.27) higher risk for incident CVD, and the participants with the highest quartile of TyG index had a 54% (HR: 1.54; 95% CI: 1.29, 1.84) higher risk of CVD compared to those in the lowest quartile. SBP significantly modifies the association between the TyG index and CVD, with higher HRs for CVD observed in those with optimal and normal SBP. SBP partially mediated the associations between the TyG index with CVD. The results were generally consistent among participants with varying pulse pressure statuses rather than diastolic BP statuses. Conclusions The associations between the TyG index and CVD were modified by BP status, with greater HRs for CVD observed among those who had SBP < 130mmHg. SBP can partially mediate the association between the TyG index with CVD, highlighting the importance of early screening for the TyG index to identify at risk of hypertension and CVD.