No clear explanation for the difference, study says
THURSDAY, May 20 (HealthDay News) -- The incidence of the most common form of stroke has decreased significantly among whites but has increased slightly among blacks, according to a new regional survey designed to be representative of the United States as a whole.
Data from the Greater Cincinnati/Northern Kentucky Stroke Study showed an overall drop of 11.6 percent between 1999 and 2005 in the incidence of ischemic strokes, those caused by blood clots blocking a brain artery.
About 80 percent of strokes are ischemic. The others are hemorrhagic, caused by a burst blood vessel. The survey found no change in the incidence of hemorrhagic stroke.
A breakdown of the data showed a 14.4 percent decrease among white residents of the region, but a 4.6 percent increase among black residents, a rise that did not quite reach statistical significance.
The death rate for those who had ischemic strokes remained the same, about 10 percent, the survey found.
The good news from the survey is the overall decrease in incidence of stroke, said study author Dr. Dawn Kleindorfer, an associate professor of neurology at the University of Cincinnati. "This is the first time we've ever seen that," she said.
The bad news, of course, was the increase among blacks, who already had a significantly higher incidence of stroke.
There is no ready explanation for the findings, since the survey was designed just to measure incidence -- rather than underlying causes -- of stroke, Kleindorfer said. The most likely explanation for the overall decrease is better treatment of risk factors such as high blood pressure, obesity and high cholesterol levels, she said.
The reason for the difference between whites and blacks is also a matter of speculation, Kleindorfer said. "There are a lot of features that the survey cannot answer -- severity of the stroke, acce
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