What Your Blood Type May Say About Your Stroke Risk

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Stroke patient with doctor
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Your blood type may be linked to your risk of having a stroke before age 60, according to a new scientific analysis.

It found that people with blood type A had a 16% greater risk of having an early-onset ischemic stroke compared with other blood types.

Meanwhile, those with type O — which is the most common blood type — had a 12% lower risk.

The researchers defined an early-onset stroke as one that happens before the age of 60. An ischemic stroke is one caused by a blood clot preventing blood from reaching the brain; it is by far the most common type of stroke.

The findings were published in Neurology, the medical journal of the American Academy of Neurology.

They were based on a review of 48 different genetic studies from across North America and several other continents. These studies provided researchers with data on about 17,000 stroke patients and, for comparison, 600,000 healthy patients who had never had a stroke.

Researchers looked at chromosomes (a component of DNA that contains genes) to see if they could find genetic variations that might be associated with a stroke. They identified a link between early stroke and a gene that determines whether a person has blood type A, AB, B or O.

After accounting for sex and other factors, the researchers determined that people with type A had a 16% greater risk, and those with type O had a 12% lower risk, of early stroke compared with people with other blood types.

In addition to the findings about blood types A and O, the researchers found a link between having a stroke after age 60 and blood type B, although it was a much weaker connection.

If you’re wondering why people with a certain blood type might be more likely to have a stroke, science doesn’t have an answer just yet.

One of the lead authors of the study — Dr. Steven J. Kittner, a professor of neurology at the University of Maryland School of Medicine — explains:

“We still don’t know why blood type A would confer a higher risk, but it likely has something to do with blood-clotting factors like platelets and cells that line the blood vessels as well as other circulating proteins, all of which play a role in the development of blood clots.”

He added that follow-up studies are needed to determine exactly how blood type affects stroke risk.

To learn about a possible stroke risk factor that, unlike your blood type, is actually within your control, check out “Eating This Kind of Fat May Increase Your Stroke Risk.”