Examining the Linear Association Between Blood Pressure Levels and Cardiovascular Diseases in the Absence of Major Risk Factors in China

Background: Many studies demonstrate a J-shaped association between blood pressure and cardiovascular diseases (CVDs), but the findings are plagued by confounding from other traditional cardiovascular risk factors (CVRFs). Our aims were to examine the associations of systolic blood pressure (SBP) and diastolic blood pressure (DBP) levels with CVD in individuals without major CVRFs and whether there were thresholds for the association. Methods: In the 4C study (China Cardiometabolic Disease and Cancer Cohort), 36 042 CVRF-free participants without CVD, diabetes, dyslipidemia, hypertension, or smoking were identified during 2011 to 2012. Among CVRF-free participants, 17 476 CVRF-preferable individuals with better glycemic (fasting glucose, <110 mg/dL; 2-hour post-load glucose, <140 mg/dL) and lipid profile (total cholesterol, <200 mg/dL; LDL [low-density lipoprotein] cholesterol, <130 mg/dL) were selected. The total person-years of follow-up for CVRF-free subjects and CVRF-preferable subjects were 130 147 and 63 573 person-years, respectively. Information on the development of major CVDs was collected during 2014 to 2016. Cox proportional hazard models were performed to estimate the risks for incident CVD by SBP and DBP groups, respectively. Results: We found that both baseline SBP and DBP presented significantly linear associations with CVD risks in CVRF-free and CVRF-preferable participants. There is significant increase in the CVD risk among CVRF-free participants with baseline SBP level of 110 to 119 mm Hg (hazard ratio, 1.79 [95% CI, 1.19–2.71]), 120 to 129 mm Hg (hazard ratio, 2.03 [95% CI, 1.36–3.03]), and 130 to 139 mm Hg (hazard ratio, 2.15 [95% CI, 1.40–3.28]) compared with SBP <110 mm Hg. Significant increases were also observed for DBP level of 80 to 89 mm Hg (hazard ratio, 1.43 [95% CI, 1.03–1.97]) compared with DBP <70 mm Hg. Similar results were observed in CVRF-preferable participants. Conclusions: SBP and DBP with levels currently considered normal were significantly and linearly associated with incident CVD without thresholds above 110/70 mm Hg among Chinese adults without major CVRFs.