Blood type can affect chances of stroke, finds study

If your blood type is 'O' – the most common type – it could help you against the risk of getting a stroke. But if your blood type is A, B, or AB, be extra careful, warns a new study.

The large, long-term study presented on Wednesday at a meeting of the American Heart Association (AHA) in Orlando, Florida suggests that people with AB and women with B type blood are most at risk.

The research can't prove such a link; but it fits with other work tying A, B and AB to more risk of blood clots in the legs and heart attacks. Blood type O also has been associated with an increased risk of bleeding, which implies less chance of clots, the cause of most strokes.

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

"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.