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.
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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 daily.
After a month, the investigators analyzed the RNA in blood taken from volunteers.
“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 to aspirin.
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 Vascular Specialists.
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.”