Stroke Risk Tied To Blood Type
November 17, 2011

Stroke Risk Tied To Blood Type

A study, led by Brigham And Women's Hospital´s Dr. Lu Qi, was presented this week at an American Heart Association conference and compares blood type with the risk of stroke.

Researchers compiled data for over 20 years on 90,000 men and women in two observational health studies. There is no direct link but along with other studies, there are patterns emerging tying A, B and AB to increased risk of blood clots in the legs and heart attacks.

Blood type O also has been tied to an increased risk of bleeding, which implies less chance of clots, the cause of most strokes.

Researchers discovered that AB blood type was associated with a 30 percent greater risk of ischemic stroke, which accounts for 90 percent of stroke total, said Qi. In women, having type B blood was associated with a 17 percent greater risk of all types of stroke, reports Marni Jameson of the Orlando Sentinel.

“There´s increasing evidence that blood type might influence risk of chronic disease,” said one of the study leaders, Dr. JoAnn Manson, chief of preventive medicine at Harvard´s Brigham and Women´s Hospital.

“It´s not at the level where we want to alarm people and we want to make that clear. But it´s one more element of risk that people would want to know about,” and it could give them one more reason to keep blood pressure and cholesterol in line, she said.

Blood is typed through proteins on the surface of red blood cells. A pattern of immune system responses forms early in life based on them. Certain blood types may make red cells more likely to clump together and stick to the lining of blood vessels, setting the stage for a blood clot, Manson tells USA Today.

“You can´t change it, and we don´t know if it´s the blood type per se or other genes that track with it” that actually confers risk, said Dr. Larry Goldstein, director of Duke University´s stroke center. “There are other things that are more important” than blood type for stroke risk, such as smoking, drinking too much and exercising too little, he said.

A person´s RH factor, whether positive or negative, did not make a difference.

Although patients can´t change their blood types, researchers said they hoped the findings would encourage those with a higher-risk blood type to be even more careful to control their other stroke-risk factors.


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