Some blood types appear to be linked to a higher risk for stroke than others said researchers presenting the results of their study at the American Heart Association’s Scientific Sessions 2011 in Orlando, Florida, on Wednesday.

Co-senior author Dr. JoAnn Manson, Chief of the Division of Preventive Medicine at Harvard’s Brigham and Women’s Hospital, and Professor of Epidemiology at Harvard School of Public Health , and colleagues examined the link between the human blood group ABO and stroke risk.

ABO includes blood types A, B, AB and O.

Drawing from two large observational studies involving more than 90,000 men and women followed for over 20 years, the researchers found that:

  • Blood type B was linked to a 17% increased risk of stroke in women, but not in men.
  • Blood type AB was linked to a 29% increased risk of ischemic stroke among men and women.

An ischemic stroke is caused by blockage to a blood vessel in the brain. Other types of stroke include hemorrhagic stroke, when a weakened blood vessel ruptures, and Transient Ischemic Attack (TIA or “mini stroke“), caused by a temporary clot.

When the researchers compared blood type AB to type O they found it was linked to a 28% higher risk of stroke in women and a 32% higher risk of stroke in men.

Differences in blood type reflect differences in the glycoproteins on the surface of red blood cells, which in turn, affects how the immune system develops. Manson suggested this source of variation may affect stickiness of red blood cells, so some types form clumps and clots more easily than others, reports the Associated Press.

Although we can’t change people’s blood type, knowing this kind of information may help identify people at these moderately higher risks for stroke, said the researchers, who suggest people with the higher risk blood types have their other risk factors assessed so they know their overall risk profile, and from that may follow a recommendation to keep to a more intensive, healthy lifestyle and diet.

Manson told the media that these links are not at the level that should alarm people, but it could give them one more reason to keep blood pressure and cholesterol in line.

Written by Catharine Paddock PhD