Hypertension is a well-known risk factor for cardiovascular disease (CVD), but whether prehypertension is also a risk factor is less clear. A new meta-analysis by Dingli Xu of Southern Medical University, Guangzhou, China and colleagues published in BMC Medicine has shown that prehypertension is a risk factor for CVD.
Prehypertension is defined as a systolic blood pressure of between 120 and 139 mm Hg or a diastolic blood pressure of between 80 and 89 mm Hg and was proposed as a new blood pressure category in 2003 in the seventh report of the Joint National Committee on Prevention, Detection, Evaluation and Treatment of High Blood Pressure. Previous studies have found its incidence to be between 30 and 50 percent, however its existence as an independent risk factor for CVD has been controversial and it is not included in all hypertension guidelines. Many individuals with prehypertension have at least one other risk factor for CVD and studies have shown conflicting results as to whether prehypertension itself is an independent risk factor for CVD or whether the increased risk is due to other confounding cardiovascular risk factors.
Xu and colleagues conducted a meta-analysis of prospective cohort studies to examine the association between prehypertension and composite CVD, coronary heart disease and stroke incidence. They identified 19 articles meeting their inclusion criteria after searching three major databases for publications up to December 2012, as well as conference proceedings and the reference lists of potentially relevant studies. After controlling for multiple CVD risk factors, they found a significant association between prehypertension and incidence of CVD. These results were consistent across age, gender and ethnicity. The risk was highest in those with high-range prehypertension (130-139/85-89 mm Hg), but even low-range prehypertension (120-129/80-84 mm Hg) was associated with an increased risk of CVD. Based on their analysis the researchers estimate that elimination of prehypertension could prevent 15.9 percent of CVD cases, 14.6 percent of coronary heart disease cases and 19.6 percent of stroke cases.
Given these findings and the high incidence of prehypertension, a successful intervention to reduce prehypertension could have major public health benefits in the primary prevention of CVD. The researchers suggest healthcare professionals consider lifestyle interventions in individuals with prehypertension, in particular those with additional CVD risk factors.