Objectives: Quantitative associations between prehypertension or its two separate blood pressure (BP) ranges and cardiovascular disease (CVD) or all-cause mortality have not been reliably documented. In this study, we performed a comprehensive systematic review and meta-analysis to assess these relationships from prospective cohort studies.
Methods: We conducted a comprehensive search of PubMed (1966-June 2012) and the Cochrane Library (1988-June 2012) without language restrictions. This was supplemented by review of the references in the included studies and relevant reviews identified in the search. Prospective studies were included if they reported multivariate-adjusted relative risks (RRs) and corresponding 95% confidence intervals (CIs) of CVD or all-cause mortality with respect to prehypertension or its two BP ranges (low range: 120-129/80-84 mmHg; high range: 130-139/85-89 mmHg) at baseline. Pooled RRs were estimated using a random-effects model or a fixed-effects model depending on the between-study heterogeneity.
Results: Thirteen studies met our inclusion criteria, with 870,678 participants. Prehypertension was not associated with an increased risk of all-cause mortality either in the whole prehypertension group (RR: 1.03; 95% CI: 0.91 to 1.15, P = 0.667) or in its two separate BP ranges (low-range: RR: 0.91; 95% CI: 0.81 to 1.02, P = 0.107; high range: RR: 1.00; 95% CI: 0.95 to 1.06, P = 0.951). Prehypertension was significantly associated with a greater risk of CVD mortality (RR: 1.32; 95% CI: 1.16 to 1.50, P<0.001). When analyzed separately by two BP ranges, only high range prehypertension was related to an increased risk of CVD mortality (low-range: RR: 1.10; 95% CI: 0.92 to 1.30, P = 0.287; high range: RR: 1.26; 95% CI: 1.13 to 1.41, P<0.001).
Conclusions: From the best available prospective data, prehypertension was not associated with all-cause mortality. More high quality cohort studies stratified by BP range are needed.