July 04--Nearly 60 million Americans take aspirin every day to help prevent
heart attacks and stroke, but new research from Duke University shows aspirin
may not be fully effective for 10 to 15 percent of the population.
A study published Wednesday in the online Journal of the American College of
Cardiology reports that a blood-based test of gene activity was able to detect
"aspirin resistance," which causes the cardiovascular system to be less
responsive to traditional aspirin therapy.
"We have seen a substantial number of people who take aspirin for prevention
come back in with heart attacks and strokes, so we knew it wasn't working in
some people," said Geoffrey S. Ginsburg, senior author and director of genomic
medicine at Duke's Institute for Genome Sciences & Policy. "We wanted to look at
that under controlled conditions."
About 25 to 30 percent of patients using aspirin therapy eventually have strokes
or heart attacks, he said. Genetics, environmental conditions and behavior
patterns all are known to play a role in cardiovascular health.
The Duke study looked at three groups of participants -- two made up of healthy
volunteers, and one made up of volunteers with heart disease who were being seen
at outpatient cardiology practices.
The healthy volunteers received 325 mg of aspirin daily, equal to a single
adult-strength pill, for about a month. Volunteers with heart disease were
already assigned to a low-dose aspirin therapy regimen, taking less than 100 mg
After a month, the investigators analyzed the RNA in blood taken from
"We found that it does work to a certain degree in everybody, but it works
better on some people and less well on other people," Ginsburg said. "And this
test was a way of measuring that."
Deepak Voora, assistant professor of medicine at Duke and lead author of the
study, said the RNA test devised for the research project identified a
biological marker -- or genetic sign -- that indicates how someone will respond
For most, a good idea
Unlike other drugs for cardiac disease prevention, such as blood-pressure or
cholesterol-lowering medications, tests currently available for aspirin response
levels are rarely offered because they are complex and available only at
specialized testing centers, Voora said.
"One of the potential benefits of our findings is that through the use of this
biomarker, we have the possibility of developing a diagnostic test based out of
whole blood that could be run at a commercial lab and come back to a physician
to give an indication of the patient's response," he said.
According to Ginsburg, the marker could also give cardiologists a way to more
precisely measure a patient's response to aspirin and then consider adjusting
the dose or switching the patient to another drug that could be more effective.
Examining genetic material for biological receptivity to certain treatments may
one day be a routine process, said Ben Walker, a cardiologist with Rex Heart and
In the meantime, he will continue to recommend low-dose aspirin to patients who
are at an elevated risk of heart attack or stroke.
"For patients at risk, and who show no signs of bruising or bleeding while on
aspirin therapy, it's a good idea," Walker said.
But for some patients, particularly those who have few or no risk factors for
cardiovascular disease, the risk of bruising and bleeding excessively due to
aspirin's blood-thinning qualities may be enough to outweigh the benefits of
aspirin therapy, Voora said.
The Duke research indicates that aspirin may function in ways that have not been
explored. Discovery of the aspirin-related biomarker may lead to better
predictions of whether someone is at high risk of heart attack, even while
taking aspirin, Ginsburg said.
The research team plans to look further into that question, he said.
"We know some people don't respond to aspirin, and that lack of response is
associated with heart attacks and strokes," Ginsburg said.
Whether giving aspirin at higher doses might generate a better response is
another question that likely will be explored.
"Someone may need three or four times the usual dose or take a non-aspirin-type
drug instead," Ginsburg said. "It's another step in more personalized medicine."
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