Previous studies estimate that between 40 and 60 percent of adults aged 75 and older in the U.S. and Europe take aspirin or other antiplatelet drugs daily to prevent heart attack or strokes. Lifelong treatment with these drugs is recommended for patients who have previously had a heart attack or stroke -- a regimen referred to as secondary prevention.
However, this advice is based on trials mostly done in patients younger than 75, the researchers point out, with a follow up of only a few years. Past research has shown a link between antiplatelet treatment and upper gastrointestinal bleeding
"We have known for some time that aspirin increases the risk of bleeding for elderly patients," the lead author of the study, Professor Peter Rothwell of the University of Oxford in the U.K., said in a statement. "But our new study gives us a much clearer understanding of the size of the increased risk and of the severity and consequences of bleeds."
The study followed 3,166 patients in the U.K. who had previously had a stroke or heart attack and were prescribed antiplatelet drugs (mostly aspirin). Half of the participants were aged 75 or older at the start of the study.
Over a 10-year period, 314 patients were admitted to hospital for bleeding.
Patients under the age of 65 taking daily aspirin were admitted to the hospital at a rate of 1.5 percent. For patients 75 to 84, the annual rate rose to approximately 3.5 percent, and to 5 percent for patients over 85.
The risk of disabling or fatal bleeding also increased with age. For patients aged under 65, the annual rate of life-threatening or fatal bleeds was less than 0.5 percent, but for patients aged 75-84, the rate rose to approximately 1.5 percent. That number rose to nearly 2.5 percent for patients aged 85 or over.
The authors emphasize that suddenly stopping any medication, including a daily aspirin regimen, can come with a number of risks and they advise speaking with a doctor first before making any changes.
They conclude that proton-pump inhibitors (heartburn drugs) could help if they are co-prescribed with an aspirin regimen, citing previous studies that show these drugs could reduce upper gastrointestinal bleeding by 70 to 90 percent in patients receiving long-term treatment with antiplatelet drugs.
"While there is some evidence that long-term PPI use might have some small risks, this study shows that the risk of bleeding without them at older ages is high, and the consequences significant," Rothwell said. "In other words, these new data should provide reassurance that the benefits of PPI use at older ages will outweigh the risks."
But not all experts agree.
Evelina Grayver, M.D., director of the cardiac care unit at North Shore University Hospital, in Manhasset, New York, warns that "proton pump inhibitors are not benign medications."
"Proton pump inhibitors change the acidity within the stomach walls and that can sometimes interfere with the appropriate absorptions of some medications, aspirin being one of them," she told CBS News. "If patients don't have any significant history of gastritis, ulcers, bleeds in the past, that has to be considered at length with their physician as to whether or not they actually need to be on extra medication like a proton pump inhibitor."
Grayver also emphasized that the study should not frighten people over the age of 75 currently taking daily aspirin to stop without talking to their doctor first.
"Every single patient who is on aspirin needs to understand the reason why they are on aspirin," she said. "For example, patients who have a history of coronary artery disease and have had stents in the past, those patients need to be on aspirin lifelong. The indication for why the patient is on aspirin is incredibly important to understand."
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