Blood pressure, body mass index and risk of cardiovascular disease in Chinese men and women

Background: It is still uncertain whether increased blood pressure (BP) has a stronger effect on the risk of cardiovascular disease (CVD) in lean persons than in obese persons. We tested it using a data set collected from a large cohort of Chinese adults. Methods: Systolic and diastolic BP, body mass index (BMI) and other variables were measured in 169,871 Chinese men and women >= 40 years of age in 1991 using standard protocols. Follow-up evaluation was conducted in 1999-2000, with a response rate of 93.4%. Data were analyzed with Cox proportional hazards models. Results: After adjusted for age, sex, cigarette smoking, alcohol consumption, high school education, physical inactivity, geographic region, and urbanization, we found that the effects of systolic or diastolic BP on risk of CVD generally increased with the increasing BMI levels (underweight, normal, overweight, and obese). For example, hazard ratios (HRs) and 95% confidence interval (CI) per 1- standard deviation (SD) increase in systolic BP within corresponding BMI levels were 1.27(1.21-1.33), 1.45(1.41-1.48), 1.52 (1.45-1.59) and 1.63 (1.51-1.76), respectively. Statistically significant interactions (P < 0.0001) were observed between systolic BP, diastolic BP and BMI in relation to CVD. In baseline hypertensive participants we found both obese men and women had higher risk of CVD than normal-weight persons. The multivariate-adjusted HRs(95% CI) were 1.23(1.03-1.47) and 1.20(1.02-1.40), respectively. Conclusion: Our study suggests that the magnitude of the association between BP and CVD generally increase with increasing BMI. Hypertension should not be regarded as a less serious risk factor in obese than in lean or normal-weight persons in Chinese adults.