Thursday, September 2, 1999 Published at 23:28 GMT 00:28 UK
High doses of aspirin linked to strokes
Scientists have questionned the benefits of aspirin
Taking aspirin to ward off strokes may be counter-productive in some cases, scientists have warned.
Aspirin thins the blood and is known to reduce the risk that people who have survived heart attacks and strokes will suffer a recurrence.
But doctors are divided over the benefits of routine use of the drug by healthy people with no history of cardiovascular disease.
Now researchers have now found that while low doses of aspirin help prevent some strokes, high doses may actually increase the risk of stroke for some patients.
According to a study published in Stroke: Journal of the American Heart Association, while aspirin can reduce a woman's risk of ischemic stroke, taking more than 15 aspirin tablets per week doubles the risk of developing a haemorrhagic stroke.
Ischemic stroke, the most common form of the disease, is caused by blood clots or other blockages in the arteries which restrict blood flow to the brain.
Haemorrhagic strokes occur when a blood vessel or vessels inside the brain ruptures and bleeds, and is more likely to be fatal than an ischemic stroke.
Lead author JoAnn Manson, professor of medicine at Harvard Medical School and Brigham and Women's Hospital, said the study found that the high doses of aspirin were a particular risk among older women and those with high blood pressure.
Researchers at Harvard Medical School and Brigham and Women's Hospital in Boston examined aspirin use and stroke risk in 79,319 healthy women ages 34-59.
Participants were monitored over a 14-year period from 1980 to 1994 during which 295 ischemic strokes and 100 haemorrhagic strokes were recorded.
Women who took low doses of aspirin (one to six tablets per week) had a lower risk of ischemic stroke, whereas women who took higher doses of aspirin (more than 15 tablets per week) were approximately twice as likely to suffer haemorrhagic strokes.
The risk of haemorrhagic stroke was tripled in older women with high blood pressure who took more than 15 aspirins per week compared to women who did not take aspirin or took lower doses.
Professor Manson said: "This study indicates that it may be a good news-bad news situation in terms of the primary prevention of stroke.
"If low doses of aspirin reduce the risk of ischemic stroke in healthy individuals, this is important, since it is the most prevalent form of stroke. On the other hand, our findings suggest that taking too much aspirin could be dangerous."