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The risk of developing a stroke depends on blood type
Last reviewed: 01.07.2025
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Scientists suspect that certain blood types are associated with an increased risk of stroke. This is the conclusion reached by researchers from Harvard University at Brigham and Women's Hospital, whose report was presented at the 2011 American Heart Association Scientific Conference in Orlando.
Study author Dr. Joanne Manson and colleagues examined the link between human ABO blood type and stroke risk.
ABO includes blood groups A (II), B (III), AB (IV) and O (I).
Based on two large studies involving more than 90,000 men and women over more than 20 years, scientists found that:
- Blood type B was associated with a 17% increased risk of stroke in women but not in men.
- Blood type AB was associated with a 29% increased risk of ischemic stroke in men and women.
Ischemic stroke occurs when a blood vessel in the brain becomes blocked. Hemorrhagic stroke occurs when a weakened blood vessel ruptures. Transient ischemic attacks (TIAs or "mini-strokes") occur when a blood vessel becomes blocked by a temporary clot.
When they looked at blood type AB with type O, they found that women with blood type AB had a 28% higher risk of stroke, while men had a 32% higher risk.
The differences in blood types reflect differences in the glycoproteins on the surface of red blood cells, which in turn affect the immune system. Dr. Manson hypothesized that these changes may affect the stickiness of red blood cells, so that some blood types form clots and thrombi more easily than others.
Although we can't change people's blood types, knowing this kind of information can help identify people at high risk of stroke, the researchers say. Doctors need to carefully identify other risk factors in people with the risk group to prevent strokes in a timely manner.