Prehypertension is clinical category created by experts in 2003 to describe patients whose blood pressure was elevated, but still considered within normal range. Hypertension or abnormally high blood pressure is a major risk factor for cardiovascular disease and strokes, but much less is known about the health threat posed of prehypertension, which is defined by a systolic pressure reading between 120 and 139 mmHg (the top number) and a diastolic reading between 80 and 89 mm Hg (the bottom number)
“The experts reasoned that, generally speaking, the higher the blood pressure, the greater the risk of death and disease, possibly starting from within the normal blood range,” said Bruce Ovbiagele, MD, professor of neurosciences at UC San Diego School of Medicine and senior author of the study.
However, Ovbiagele said, conclusive evidence was lacking, “so we decided to compile all the published studies in the scientific literature to date, and using statistical techniques find out if there is indeed a higher risk of future stroke in people with prehypertension, the extent of that risk, and whether particular characteristics were associated with higher stroke risk.”
Article source: http://www.medindia.net/news/Stroke-Risk-High-Even-With-Elevated-but-normal-Blood-Pressure-Levels-91269-1.htm