For Women Only: Aspirin Cuts First Stroke Risk by 17%

DALLAS -- Aspirin appears to be effective for primary prevention of stroke in women, but not in men, according to the findings of a metaanalysis presented by Dr. David L. Brown at the annual scientific sessions of the American Heart Association.

"For women with no history of cardiovascular disease, aspirin reduces the risk of total stroke by reducing the risk of ischemic stroke. Among men, aspirin slightly increases the total risk of stroke because it has no effect in reducing ischemic strokes and actually increases the risk of hemorrhagic stroke," explained Dr. Brown, professor of medicine at the State University of New York at Stony Brook.

Aspirin's role as an effective, safe, and inexpensive agent for secondary prevention of stroke in patients with known cardiovascular disease is firmly established. But the same can't be said regarding aspirin for primary prevention of stroke, an unresolved issue.

To shed new light on the subject, Dr. Brown performed a metaanalysis of six randomized controlled primary prevention trials. Three included only men, the largest being the 22,071-subject Physicians' Health Study. The 18,790-subject Hypertension Optimal Treatment (HOT) study included both men and women, whereas the nearly 40,000-participant Women's Health Study included women only. Various aspirin-dosing regimens employed in the trials included 75 mg/day, 100 mg every other day, and 500 mg/day.

Among 51,342 randomized women, aspirin therapy was associated with a significant 17% reduction in overall stroke risk. This was achieved through a 24% reduction in risk of ischemic stroke and a nonsignificant 7% increase in risk of hemorrhagic stroke.

In the 44,114 randomized men included in the metaanalysis, however, aspirin therapy was associated with a nonsignificant 13% increase in overall risk of strokes. This was the result of a disturbing 67% increase in risk of hemorrhagic strokes coupled with aspirin's lack of effect upon the risk of ischemic strokes in men.

As this study is vulnerable to the biases inherent in metaanalysis, the results must be viewed as generating hypotheses, rather than as definitive, Dr. Brown stressed. One hypothesis for the observed gender disparity is genetic factors. "But I think you also have to look at the prevalence of stroke risk factors," Dr. Brown added. "Hypertension is known to be more common in women, and it may just be that because women have a higher risk they see more benefit from the aspirin. But the explanation is completely unknown at this time, to be honest."