For decades, healthy patients were told to take a low-dose aspirin as a precaution to help prevent heart problems, but the guidelines changed this year. For patients who have had a heart attack, stroke or open heart surgery, a daily aspirin is still recommended and can be a lifesaver. But the blood-thinning effect from aspirin could cause a major bleeding event, so for many healthy patients, the daily aspirin habit was not worth the risk.
A new study published in the medical journal Annals of Internal Medicine on Monday came to a different conclusion.
The study found that aspirin reduces the risk of heart problems for at-risk patients and for some patients without a known risk of cardiovascular disease. The researchers concluded that the benefits of aspirin outweigh the harms of bleeding, if you compared the risk of death from one bleeding event compared to the risk of hospitalization or death from a cardiac event.
At least 12.1% of men and 2.5% of women without a history of heart problems got a net benefit from five years of aspirin treatment, the study found. The percent benefit increased even more if you compared the risk for two bleeding events to two cardiovascular events.
Researchers figured this out by looking at data from more than 245,000 healthy adults ages 30 to 79 years old in New Zealand.
"We classified each individual within the study as benefiting from aspirin if the number of [cardiovascular disease] events prevented was greater than the number of bleeding events, were 1,000 people with the same characteristics as that individual to be treated with aspirin for 5 years," said author Vanessa Selak, a senior lecturer in the section of epidemiology and biostatistics at the School of Population Health at the University of Auckland.
While the authors conclude that for some people without heart disease, aspirin is "likely to result in net benefit," they caution that more research will be needed see if this would apply to people who live outside of New Zealand. They also didn't look at aspirin use in people older than 79.
The authors of the study don't make an argument to change the current guidelines, which were created for the United States by the American College of Cardiology and American Heart Association.
The study adds that while "aspirin is likely to result in a net benefit" that it's "difficult" to make a general recommendation about it.
Kevin McConway, an emeritus professor of applied statistics at The Open University, agrees with their caution.
"The methods of estimating the risk of [cardiovascular disease] and of major bleeds are based on data from New Zealand, and might give inappropriate figures for the risks in other populations," McConway, who was not affiliated with the research, told the Science Media Centre in the UK. "It would be wrong simply to take over the New Zealand results to other populations without further research."
Similar findings, different interpretation
Earlier research has shown that taking a daily low-dose aspirin is associated with an increased risk of bleeding in the skull.
Dr. Amit Khera, a professor of medicine in the division of cardiology at UT Southwestern Medical Center who helped write the latest guidelines from the American Heart Association and the American College of Cardiology concerning aspirin, said these findings are similar to the trio of 2018 studies used to create the current US guidelines.
While the findings are similar, those studies came to a different conclusion and argued that a daily aspirin regimen provided no significant health benefit for older adults and may cause harm. What's largely different, Khera said, is the interpretation of the risk of a bleeding event. Unlike the authors of the current study, he thinks the harm is too great.
"This isn't a nosebleed, these are serious bleeding events that require hospitalization and transfusions," said Khera.
Still, a recent study found that millions of US adults who never had cardiovascular disease are still taking aspirin.
"It used to be when patients were considering using daily aspirin we would say generally yes, occasionally no. Now when people ask, it is a generally no, you shouldn't take it, and occasionally it's a yes. It's a much more fine balance now," Khera said. "It can help people who have had heart attacks and strokes, but generally healthy people, for most people, it does not do them any favor, taking aspirin."
Instead, doctors urge patients to adopt healthy lifestyle habits like not smoking and controlling blood pressure and cholesterol through exercise and diet.
Selak, who wrote the new study, emphasizes the fine line in this decision.
"There is clearly a benefit of aspirin in terms of reducing the risk of [cardiovascular disease] events, based on a recently published meta-analysis of all relevant trials of aspirin among people without established CVD," Selak said. "The challenge is that aspirin also increases the risk of major bleeds.
"What our study has shown is that there are people who are likely to benefit overall from aspirin, taking into account the bleeding harms, but a personalized prediction of benefits and harms is needed in order to identify these people."