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Aspirin Reduces Stroke Risk in Women, Not Men

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Duke Health News 919-660-1306

DALLAS -- A meta-analysis of more than 95,000 patients has
shown that aspirin can significantly reduce the risk of stroke
in women, but it appears to have no protective effect in men,
according to a new analysis by Duke University Medical Center
cardiologists.

Additionally, the researchers found that aspirin increases
the risk of bleeding, or hemorrhagic, strokes in men with no
effect on women. For the more common form of stroke known as
ischemic stroke, in which blood flow to a portion of brain is
blocked, aspirin had no effect on men but reduced the incidence
in women.

The seemingly conflicting results of this study, along with
the results of other studies, should lead to more intensive
research into the differences between the genders when it comes
to cerebrovascular disease and drugs use to prevent it, the
researchers said. They emphasized that both healthy men and
women who can tolerate aspirin should be taking the medication,
since this analysis demonstrated its effectiveness in
preventing strokes in women, and it is already known to reduce
heart attacks in men.

"While we've known that aspirin is effective in preventing
stroke in patients who already have cerebrovascular disease,
very little is known about its abilities as a primary
prevention method in otherwise healthy people," said Duke
cardiology fellow Jeffrey Berger, M.D., who presented the
results of his analysis Nov. 14, 2005, at the annual scientific
sessions of the American Heart Association in Dallas.

"Until the advent of the Women's Health Study (WHS),
clinical trials included primarily men and found that aspirin
had a positive effect in reducing the risk for heart attacks,
but had no effect on stroke," Berger continued. "So when the
WHS found a positive effect for aspirin on stroke prevention in
women, it raised the question of whether or not gender has an
impact on aspirin's ability to reduce the risk of stroke."

In addition to the small numbers of women studied, these
earlier clinical trials did not distinguish between the two
markedly different types of stroke -- ischemic and
hemorrhagic.

During a stroke, brain cells are either damaged or killed,
with the effects on the patient depending on the size of the
damage and where in the brain the damage occurs. The ischemic
form of stroke, in which arteries supplying blood to the brain
are blocked, represents about 83 percent of all strokes. The
hemorrhagic form of stroke, which tends to have more serious
consequences for the patient, occurs when blood vessels within
the brain burst, leading to a potentially deadly buildup of
blood within the brain.

For his analysis on the effects of gender on aspirin's
ability to prevent stroke, Berger combined the data from six
different randomized clinical trials, including the WHS, which
yielded a total of 95,456 patients, none of whom had coronary
artery disease. Of that total, 51,342 were women. The trials
all involved the comparison of low-dose aspirin versus placebo
for the primary prevention of cardiovascular disease.

"Among the women who were involved in these trials, the use
of aspirin was associated with a statistically significant 17
percent reduction in the risk of stroke," Berger said. "For the
men, aspirin use was associated with a non-significant 13
percent increase in stroke risk."

When Berger concentrated on ischemic stroke, he found that
aspirin use was associated with a significant 24 percent
reduction in risk in women, compared to no effect for men. For
hemorrhagic stroke, the trends were reversed: aspirin had no
significant effect on women, but in men, aspirin was associated
with a significant 69 percent increase in risk.

"The reasons or mechanisms behind any gender-based
differences in the ability of aspirin to prevent stroke is
unclear and requires further investigation," Berger said. "The
bigger question this study raises is that there may be
biological differences in how the genders response to other
drugs we prescribe patients. This study raises the question for
one drug – aspirin."

Berger said that the findings of this analysis should
provide a scientific basis for physicians to prescribe aspirin
as a preventative measure for those women who do not suffer
from the potential gastrointestinal side effects of the
drug.

"As opposed to the situation with men, aspirin tends to be
under-prescribed for women," Berger said. "There is no reason
for this to be the case – aspirin is effective, it is
inexpensive and easily available."

According to the American Stroke Association, about 700,000
Americans will suffer a stroke each year, with about 163,000 of
them dying, making it the third leading cause of death. About
60 percent of strokes are suffered by women.

Joining Berger in his analysis was his mentor, David Brown,
M.D., State University of New York Health Science Center, Stony
Brook, NY.

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