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.