Association between pre-hypertension and cardiovascular outcomes: a systematic review and meta-analysis of prospective studies.

Background: The quantitative associations between prehypertension or its separate blood pressure (BP) ranges and the risk of main cardiovascular diseases (CVDs) have not been reliably documented.
Methods: We performed a comprehensive search of PubMed (1966 to June 2012) and the Cochrane Library (1988 to June 2012) without language restrictions. Prospective studies were included if they reported multivariate-adjusted risk ratios (RRs) and corresponding 95 % confidence intervals (CIs) of desirable outcomes, including fatal or non-fatal incident stroke, coronary heart disease, myocardial infarction (MI) or total CVD events, with respect to prehypertension or its separate BP ranges (low range: 120–129/80–84 mmHg; high range: 130–139/85–89 mmHg) at baseline with normal BP (<120/80 mmHg) as reference. Pooled RRs were estimated using a random-effects model or a fixed-effects model.
Results: Twenty-nine articles met our inclusion criteria, with 1,010,858 participants. Both low-range and high-range prehypertension were associated with a greater risk of developing or dying of total CVD (low-range: RR: 1.24; 95 % CI: 1.10 to 1.39; high range: RR: 1.56; 95 % CI: 1.36 to 1.78), stroke (low-range: RR: 1.35; 95 % CI: 1.10 to 1.66; high-range: RR: 1.95; 95 % CI: 1.69 to 2.24) and myocardial infarction (MI) (low range: RR: 1.43; 95 % CI: 1.10 to 1.86; high range: RR: 1.99; 95 % CI: 1.59 to 2.50). The whole range prehypertension had a 1.44-fold (95 % CI: 1.35 to 1.53), 1.73-fold (95 % CI: 1.61 to 1.85), and 1.79-fold (95 % CI: 1.45 to 2.22) risk of total CVD, stroke, and MI, respectively. There was no evidence of publication bias.
Conclusions: Prehypertensive patients have a greater risk of incident stroke, MI and total CVD events. The impact was markedly different between the low and high prehypertension ranges