Patients with a history of heart disease who stopped taking a low-dose daily aspirin had a 60% increased risk of having a heart attack over the three-year follow-up, compared with patients who continued the daily aspirin, says study researcher Luis A. Garcia Rodriguez, MD, director of the Spanish Center for Pharmacoepidemiologic Research (CEIFE) in Madrid.
His study is published online in BMJ.
"Patients on low-dose aspirin for secondary prevention of cardiovascular disease should be advised that unless there is a high risk of serious bleeding or otherwise recommended by a doctor, aspirin should never be discontinued, given its overwhelming benefit [on heart health]," Garcia Rodriguez tells WebMD.
The study supports the findings of previous research, he says. However, those studies were done in patients while in the hospital. Garcia Rodriguez believes his is the first to look at non-hospitalized patients with heart disease.
The researchers analyzed information on nearly 40,000 patients from The Health Improvement Network, a large U.K. database of primary care records.
The patients, aged 50 to 84, were told by their doctors to take aspirin to prevent repeats of cardiovascular problems. The doses ranged from 75 to 300 milligrams daily.
Daily aspirin interferes with blood clotting. It reduces the clumping action of the platelets, the blood clotting cells.
During the three-year follow-up, 876 patients had a heart attack but survived. Another 346 died of heart disease, including heart attacks.
When the researchers compared current aspirin users to those who stopped, they found the 60% increased risk of nonfatal heart attack among those who stopped. It did not matter how long they had been on the aspirin.
Put in other terms, for every 1,000 patients over a one-year period, there were four extra cases of nonfatal heart attacks for those who stopped aspirin.
Patients said they stopped for various reasons, including safety concerns. One risk is internal bleeding.
The researchers did not find an increased risk between stopping aspirin and the risk of heart disease death alone.
Stopping aspirin is thought to adversely affect the platelet function, among other mechanisms, Garcia Rodriguez says.
AstraZeneca Research and Development MoIndal funded the study. CEIFE reports research funding from AstraZeneca. One co-author is an employee of AstraZeneca.
Aspirin and Heart Disease: Perspective
In an editorial accompanying the study, Giuseppe Biondi Zoccai, MD, of the University of Modena and Reggio Emilia, Modena, Italy, says the risk-benefit ratio of aspirin must be considered for individual patients.
It's also important to put the risk of stopping aspirin in perspective, he tells WebMD in an email.
"We might compare aspirin to safety seat belts. If you drive your car without using the safety seat belts, your risk of having a fatal accident is increased, but most of the time if you just are going to the mall, you come back home safely. However, given the huge amount of patients at risk and the fact that patients remain at risk lifelong, then it is easier to understand why the individual and population implications of aspirin discontinuation are so negative."
In some cases, patients are advised to stop aspirin, such as before major surgery, he says. So is there a ''safe'' window for stopping aspirin?
Biondi Zoccai cites his study and others. "We can estimate from basic studies as well as clinical studies that up to five days of aspirin withdrawal are not associated with major increases in cardiovascular risk," he says. However, the risk goes up about 8 to 10 days after the last dose, he says.