Association Between Pre-hypertension and Cardiovascular Outcomes: A Systematic Review and Meta-analysis of Prospective Studies

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. 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. 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. 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.