May 25, 2021 -- A new study found no difference in the rate of heart attack, stroke, or death between low- or high- dose aspirin in people with heart disease.

There was also no difference in the rate of serious bleeding events that required a blood transfusion.

This study involved more than 15,000 people who had heart disease. Half were told to take 81 mg of aspirin daily and half were told to take 325 mg.

W. Schuyler Jones, MD, a cardiologist and associate professor of medicine at Duke University Medical Center in Durham, NC, presented the study results May 15 at the virtual American College of Cardiology 2021 Scientific Session. They were also published online in the New England Journal of Medicine 

More than 41% of people in the higher aspirin group switched to low-dose aspirin during the study; those who stuck with the higher dose throughout seemed to do better over the long term.

"If a patient is already taking 81 mg, staying on this dose is probably right given the similar study results for the primary endpoint and that we didn't find conclusive evidence that 325 mg is better; but for patients who have tolerated 325 mg long term, then they may want to stay on this dose as it may be associated with moderate benefit," Jones told Medscape

Colin Baigent, a  professor of epidemiology and director of the Medical Research Council Population Health Research Unit at the University of Oxford, who was not involved in the study, cautioned that the high degree of switching between doses that occurred during the trial gives rise to some uncertainty about the results.  

Everyone in the study was already diagnosed with heart disease and most were taking aspirin before the trial began. Daily aspirin is generally not recommended for people who do not have heart disease, after a number of studies found that the risks of serious bleeding, outweigh the potential benefits for most.

A summary of the results in English and Spanish is available at