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Senior Citizen Health & Medicine
Aspirin and Older Women: Doesn't Stop Mental
Decline, Less Effective for Heart Disease than for Men
Two new studies continue the mystery of aspirin
therapy for women
 May
2, 2007 - A new study shows that taking aspirin for coronary artery
disease is four times more likely to be ineffective in women compared to
men with the same medical history. And, a second study finds taking low
dose aspirin does not protect older women against cognitive decline.
Historically, studies have shown that aspirin
therapy is less effective in women than in men, but it has remained
unclear how much less effective and whether this affects patient
outcomes, said Michael Dorsch, clinical pharmacist and adjunct clinical
instructor at the University of Michigan College of Pharmacy.
Dorsch is the lead author of the paper, "Aspirin
Resistance in Patients with Stable Coronary Artery Disease," which
appears online in the current Annals of Pharmacotherapy.
Originally, Dorsch and his team set out to
determine if patients with a history of heart attacks were more apt to
be aspirin resistant than those with coronary artery disease but no
history of heart attack. They found that gender and not medical history
was a predictor for aspirin resistance, Dorsch said. The results
surprised him.
"I was surprised by how big of a difference it was
for females," said Dorsch, who has appointments at the U-M Health System
and the U-M College of Pharmacy, and started the study as a resident at
the University of North Carolina. "This is another piece of information
that affirms we need more studies in women."
Aspirin therapy is a cornerstone in managing heart
disease because it inhibits blood clotting. Aspirin therapy can reduce
the risk of a nonfatal heart attack or stroke by about 23 percent, and
an estimated 20 million men and women take a low dose of aspirin
(81-325 mg daily) to control heart disease.
But despite its effectiveness, there is evidence
that aspirin is less effective in some patients, and researchers don't
really know why. This can be frightening because most doctors do not
check for aspirin resistance before prescribing aspirin therapy and
therefore presume it's working in the patient when it may not be, he
said.
There isn't enough evidence to show if people who
are aspirin resistant can simply take larger doses, but Dorsch warns
that people taking aspirin on the advice of a doctor shouldn't stop
therapy on account of these results.
Not only did the study quantify how much more
effective aspirin therapy is for men than for women, it is also the
first study that Dorsch knows of to measure aspirin resistance in men
and women with stable coronary artery disease. Previous studies have
looked at the impact of aspirin therapy on people who have had a heart
attack.
For the study, researchers randomly selected 100
patients who were visiting their cardiologist for a regularly scheduled
appointment. All had coronary artery disease but only half had a history
of heart attack. Researchers used a device called VerifyNow Aspirin
Assay to test the percentage of platelet reactivity after blood samples
were exposed to a chemical that causes clotting.
Aspirin works by causing platelet inhibition in the
blood, which means that platelets cannot stick together and this slows
the formation of blood clots that cause a heart attack or stroke.
"This does happen in women, but it doesn't happen
in as many women and it's not as effective," Dorsch said. The testing
device uses an optical sensor to "see" what percentage of the platelets
in the blood sample clump together. Anything less than 40 percent
platelet inhibition is considered aspirin resistant.
"We really don't know the mechanism," Dorsch said.
"It could be that women have a more active platelet system in the body
so it's less likely that platelet action would be inhibited."
In the future, researchers hope to look at aspirin
therapy outcomes in women only and see if those outcomes can be changed.
The majority of testing for aspirin therapy has been on men, so not much
is known about how women respond.
"Heart disease is the number one killer of women in
the United States. Future research should be aimed at finding out the
cause of this increase in aspirin resistance and the effect on outcomes
in women with heart disease." Dorsch said.
Editor's Notes: The study was funded by
the National Institutes of Health. For more on the College of Pharmacy,
visit:
http://www.umich.edu/~pharmacy/. For more on the U-M Health System,
visit:
http://www.med.umich.edu/
Low dose aspirin does not protect women against
cognitive decline
In the second study, published online at bmj.com,
researchers conclude that taking low dose aspirin does not protect older
women against cognitive decline.
Identifying ways to prevent dementia is a public
health priority. Evidence suggests that aspirin and other
anti-inflammatory drugs may protect against dementia, but data from
randomised studies to date have been inconclusive. So researchers in the
U.S. decided to test the effect of long term use of low dose aspirin on
overall cognitive decline among a large sample of women.
Jae Hee Kang and colleagues at Brigham and Women's
Hospital in Boston, Massachusetts identified 6,377 women aged 65 years
or more, who were taking part in the Womens health study between 1998
and 2004.
The women were randomly divided into two groups.
Over a period of nearly 10 years, the first group took low dose aspirin
(100 mg on alternate days) and the second group took a placebo pill.
Each woman had three cognitive assessments at two year intervals to
measure general cognition, verbal memory, and category fluency.
At the initial assessment (after 5.6 years of
treatment) cognitive performance in the aspirin group was similar to
that of the placebo group. Average performance across all tests from the
first to the final assessment (after 9.6 years of treatment) was also
similar in the aspirin group compared with the placebo group. The risk
of substantial decline was also comparable between the groups.
There was some suggestion that women in the aspirin
group performed better in the category fluency test than women in the
placebo group. However, the authors stress that this result should be
interpreted with caution.
They conclude: "In this study, we observed no
apparent benefit of low dose aspirin in slowing cognitive decline over
four years. Other methods for preserving cognitive function in older
people need to be investigated."
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