Meta-analysis of cohort studies of baseline prehypertension and risk of coronary heart disease.

Prehypertension is a common condition, but the extent to which it increases the risk for coronary heart disease (CHD) is unclear. The aim of this study was to determine the association between baseline prehypertension and risk for CHD by performing a meta-analysis of prospective cohort studies. A systematic search of published research was conducted through January 2013, using electronic databases and bibliographies of retrieved reports. Studies were included if they reported multivariate-adjusted relative risks (RRs) and corresponding 95% confidence intervals (CIs) of CHD with respect to prehypertension. A random-effects model was used to combine the study-specific risk estimates. Eighteen studies, consisting of 934,106 participants and 14,952 cases, with a median follow-up period of 8.8 years, were included. Prehypertension was associated with a significantly elevated risk for CHD (RR 1.36, 95% CI 1.22 to 1.53). Eight studies consisting of 12 cohorts further provided risk estimates for low-range prehypertension (120/80 to 129/84 mm Hg) and high-range prehypertension (130/85 to 139/89 mm Hg) separately. The risk for CHD increased significantly in high-range prehypertensive populations (RR 1.53, 95% CI 1.19 to 1.97) but not in low-range prehypertensive populations (RR 1.16, 95% CI 0.96 to 1.42). In conclusion, prehypertension is associated with a significantly increased risk for developing CHD, particularly high-range prehypertension. Further well-designed randomized controlled trials are needed to clarify the efficacy of blood pressure reduction in subjects with prehypertension.