What your blood pressure does while you snooze may indicate your stroke risk.

People whose blood pressure does not decrease or "dip" by 10% or more while they are sleeping may be at increased risk for stroke, according to a new study published in the December issue of the American Journal of Hypertension.

Researchers compared the blood pressures of people who had had a stroke with those who had never suffered a stroke. "What we found was that those patients who have had a stroke are more likely not to drop their blood pressure at night," says Robert A. Phillips, MD, PhD director of hypertension and cardiac health programs at Mount Sinai School of Medicine in New York City.

Previous studies done in Europe and Asia have shown a link between so-called "nondipping" blood pressure and stroke, Phillips says, and this new study, which involved people of black, white and Caribbean Hispanic backgrounds, extends those findings.

One heart expert agrees that the new study adds to previous findings, but notes that since the participants had strokes before the study began, there is no way to know if they had nondipping blood pressure before their stroke--and if the blood pressure pattern could be used to pinpoint people at high risk for stroke.

"I think the study extends in important ways the body of knowledge, but because it was looking at people with stroke ?we must be cautious in concluding that nondipping status contributes to stroke," says Daniel Levy, MD, director of the National Heart, Lung and Blood Institute's Framingham Heart Study.

Both Levy and Phillips say that further study in this area could lead to measures that could minimize damage from stroke and heart problems.

"I think that learning more about blood pressure dynamics may help us learn more about who's at risk," Levy says.

Phillips says if findings like these continue, one day it may be possible to lower a person's blood pressure at night to reduce their stroke risk and prevent strokes, but that would be in the future, he notes.

Right now, he says, the important issue for people with high blood pressure is daytime control, since high blood pressure is a risk factor for stroke. About 70% of people in the US who have high blood pressure aren't controlling their hypertension well--day or night, Phillips says.

(From CBSHealthWatch)