Blood Type May Be Associated With Stroke Risk:
WEDNESDAY, Nov. 16 (HealthDay News) -- People with certain blood
types may be at heightened risk for stroke, a new study
Researchers analyzed data on nearly 62,000 women taking part in
the Nurses' Health Study and about 28,000 men from the Health
Professionals Follow-up Study. Participants were tracked for 20 to
Over that time, both men and women with blood type AB had a 26
percent increased risk of stroke compared to those with blood type
In women, type B was also associated with a 15 percent
heightened risk of stroke compared to women of a similar age with
type O. A similar association was not found in men.
Blood type A wasn't linked with an added stroke risk in either
gender, the investigators found.
"Blood group AB showed most consistent association with stroke," said study author Dr. Lu Qi, an assistant professor of medicine at Harvard Medical School and an assistant professor of nutrition at Harvard School of Public Health in Boston.
However, while the study did uncover an association between
blood type and stroke, it did not prove a cause-and-effect
The study was slated for presentation Wednesday at the American
Heart Association annual meeting in Orlando, Fla. Research
presented at medical meetings should be viewed as preliminary until
published in a peer-reviewed journal.
People can have one of eight possible blood types, which differs
by the presence (or lack) of certain antigens, which are part of
the immune system. Type O blood, known as the universal red cell
donor, was the most common in whites in the group studied -- about
43 percent had O, 36 percent had A, 13 percent had B and about 7.5
percent had AB. Another antigen, the Rh factor, determines whether
any blood type is either positive or negative.
Commenting on the study, Dr. Larry Goldstein, director of the
Stroke Center at Duke University and an American Heart Association
spokesman, said no one knows why certain blood types might add to
stroke risk, or even if there is actually a relationship.
It's possible that blood type is standing in for some other
factor that influences stroke risk, he noted.
"It's hard to know if blood type is a marker for something else or if there's a direct relationship," Goldstein said. "For example, maybe there is some other genetic factor that is traveling along with the blood type or that's associated with that blood type that may affect stroke risk."
In the study, researchers took into account age, smoking status
and physical activity levels, but not other factors such as
cholesterol levels or diabetes that could also influence stroke
risk, Goldstein added.
A study published in January in
The Lancet found that blood type O may offer some protection
from heart attacks. But other research looking at blood type and
disease risk haven't consistently shown an association, Goldstein
Future research will look at stroke risk and blood type among
other ethnic groups, as well as trying to figure out what
biological mechanism might explain the association, Qi added.
Learn more about blood types at the
American Red Cross.
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