An unusual study in which thousands of heart patients enrolled and monitored their health online while taking low- or regular-dose aspirin found that both doses seemed equally safe and effective in preventing additional heart problems and strokes.
But there is a big caveat: People have preferred the lower dose so much that it is unclear whether the results can show that the treatment is really equivalent, say some independent experts. Half of those who were told to take the higher dose instead took the lower dose or stopped taking aspirin altogether.
“Patients actually decided for themselves what they wanted to take because they bought the aspirin themselves,”
Still, the results show there is little reason to take the higher dose, 325 milligrams, which many doctors believe will work better than 81 milligrams of “baby aspirin,” he said.
The results were published Saturday in the New England Journal of Medicine and discussed at a conference at the American College of Cardiology.
Aspirin helps prevent blood clots, but is not recommended for healthy people who have not yet developed heart disease, as they run the risk of bleeding. Its benefits are clear to people who have already had a heart attack, bypass, or clogged arteries requiring a stent.
But the best dose is not known and the study aims to compare them in real conditions. This was the first experiment funded by the Research Center for Patient-centered outcomes, created under the Patient Protection and Affordable Care Act of 2010 to help patients make informed healthcare decisions.
About 15,000 people received invitations to join by mail, email or phone call and signed up for a website where they returned every three to six months for follow-up. A network of participating health centers provided medical information to participants from their electronic records and insurance claims.
Participants were randomly assigned to take low or regular doses of aspirin, which they bought over the counter. Almost all had taken aspirin before the study began, and 85% were already on a low dose, so “it was a very difficult task from the beginning” to get people to use the dose they were told, Virani said.
After approximately two years, about 7% of each group died or were hospitalized for a heart attack or stroke. The safety results are also similar – less than 1% have had major bleeding requiring hospitalization and transfusion.
Nearly 41% of those assigned to take the higher dose have switched to a lower one at some point, and this high degree “could mask the real difference” in safety or effectiveness, Colin Baygent, a medical scientist at Oxford University in the UK, wrote in comment in the medical journal.
One study leader, Dr. Schuyler Jones of Duke University, said the study still provides valuable guidance. If patients are taking low-dose aspirin now, “staying on that dose instead of switching is the right choice,” he said. People who are doing well with 325 milligrams now may want to continue with this and should talk to their doctors if they have any concerns.
“For new patients, we would generally recommend starting a low dose,” Jones said.
Virani said that people should remember that aspirin is a medicine and that although it is sold without a prescription, patients should not make their own decisions about its use.
“Do not change the dose or stop without talking to someone,” he warned. “This is important, especially for therapy like aspirin.”
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