Relationship between the metabolic syndrome and the development of hypertension in the Hong Kong cardiovascular risk factor prevalence study-2 (CRISPS2)

Background: The metabolic syndrome is a predictor of diabetes and coronary events. We hypothesized that it also predicts hypertension. Methods: A total of 1,944 subjects (901 men and 1,043 women; age 46 ± 12 years) from the Hong Kong Cardiovascular Risk Factor Prevalence Survey were recruited in 1995-1996 and restudied in 2000-2004. The prevalence of hypertension and factors predicting its development were determined. Results: In 2000-2004, hypertension was found in 23.2% of the men and 17.2% of the women. Of the 1,602 subjects who were normotensive at baseline, 258 subjects developed hypertension after a median interval of 6.4 years. According to the National Cholesterol Education Program (NCEP) and International Diabetes Federation (IDF) criteria, the hazard ratios associated with the metabolic syndrome were 1.89 (95% confidence interval (CI): 1.41-2.54) and 1.72 (95% CI: 1.24-2.39), respectively. The positive and negative predictive values of the metabolic syndrome for identifying subjects who will develop hypertension in this population were 34.7 and 85.4% (NCEP criteria), and 33.1 and 85.5% (IDF criteria), respectively. The development of hypertension was related to the number of components of the metabolic syndrome (other than raised blood pressure), present in men (P = 0.003) and in women (P = 0.001). Using multivariate analysis, age, baseline systolic blood pressure (SBP), body mass index (BMI), and the triglycerides/high-density lipoprotein (HDL) ratio were found to be significant predictors of the development of hypertension. Compared with optimal blood pressure, the hazards of developing hypertension associated with normal or high-normal blood pressure were 2.31 (95% CI: 1.68-3.17) and 3.48 (95% CI: 2.52-4.81), respectively. Conclusions: Blood pressure, when not optimal, is the predominant predictor of hypertension. The metabolic syndrome contributes to the risk, especially when blood pressure is optimal.