Newark, NJ - It appears that prehypertension—systolic BP of 120 to 139 and diastolic BP of 80 to 89 mm Hg—is associated with a 3.5-fold increased risk of MI and a 1.7-fold increased risk of CAD. These findings, based on an analysis of data from the Framingham Study, are published online August 4, 2005 and will be in the September 2005 issue of Stroke [1].

"For years we've been aware of two categories of blood pressure: normal blood pressure—less than 120/80 mm Hg—and hypertension—140/90 mm Hg or greater," lead study author Dr Adnan Qureshi (University of Medicine and Dentistry of New Jersey, Newark) told heartwire. "There is this gray zone in the middle, which isn't hypertension but isn't normal blood pressure, either." A little more than a year ago, the Joint National Committee on High Blood Pressure (JNC 7) identified this gray zone as a new category of blood pressure in adults, termed prehypertension.

Qureshi and colleagues aimed to see whether patients with prehypertension have an increased risk of atherothrombotic brain infarction (ABI), all strokes, MI, or CAD. They investigated a cohort of 5181 people (mean age 44+8.6 years, 45% men) from the Framingham study, which has more than 50 years of data. The team looked at 11 116 person observations with a mean follow-up of 9.9+1.0 years to determine relative risk and population-attributable risk (PAR), which is the proportion of a disease that is attributable to the exposure (prehypertension).

They found prehypertension was associated with statistically significant increases in risk of MI and CAD, but not ABI or all strokes. Stroke was less frequently seen in the whole population in general, said Qureshi. "Coronary artery disease and stroke go hand in hand, so we need more research before we can say that people with prehypertension are not at risk of stroke."

They also determined that 47% of the MI and 30% of the CAD in this population was attributable to prehypertension. But this may be overestimated, since cardiovascular risk factors cluster within individuals.

"At this point, prehypertension is not considered an indication to start antihypertensive medication," Qureshi said. "At best, we just counsel our patients to reduce weight, exercise regularly, and eat healthily, but now this study is raising the question of whether people who are prehypertensive should be treated with antihypertensive agents.

"The reason prehypertension has such a striking impact is because it's so common: 60 million people in the US have it," Qureshi told heartwire. "Even if this relationship were modest, you'd still have a huge effect on the population as a whole. . . . That's why any information on any new treatment strategies for people in this particular category is important."