Macro shot of white asprin on white.

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ANN ARBOR, Mich — More isn’t always better—at least when taking aspirin. Research from the University of Michigan shows that taking one aspirin lowers the risk of bleeding complications than taking two blood thinners. The study is a reminder that aspirin is beneficial, but only in moderation.

Aspirin carries a wide range of health benefits, and for some, it is a life-saving drug. People with past strokes, heart attacks, or a stent placed in their hearts show improved blood flow when taking aspirin. The issue arises when aspirin is paired with another blood thinner.

“We know that aspirin is not a panacea drug as it was once thought to be and can in fact lead to more bleeding events in some of these patients, so we worked with the clinics to reduce aspirin use among patients for whom it might not be necessary,” Geoffrey Barnes, MD, senior author of the study and a cardiologist at the University of Michigan Health Frankel Cardiovascular Center, explains in a press release.

The researchers examined the bleeding outcomes of 6,700 people receiving treatment at anticoagulation clinics for blood clots and irregular heart rhythms that increase stroke risk. People were prescribed the blood thinner warfarin and aspirin, even if they had no history of heart disease.

During the 2022 study, published in the journal JAMA Network Open, 46.6% of people stopped taking aspirin. Those who discontinued aspirin showed a 32.3% lower risk of bleeding complications. For every 1,000 patients, not taking aspirin prevented one major bleeding event, according to the results.

“When we started this study, there was already an effort by doctors to reduce aspirin use, and our findings show that accelerating that reduction prevents serious bleeding complications which, in turn, can be life-saving for patients,” says Dr. Barnes. “It’s really important for physicians and health systems to be more cognizant about when patients on a blood thinner should and should not be using aspirin.”

The findings coincide with other studies questioning the necessity of aspirin with other blood thinners. For example, a separate study reported more emergency room visits among people taking warfarin and aspirin for irregular heartbeats or blood clotting and more instances of major bleeding. Another research study suggested a higher risk of bleeding for people taking aspirin and direct oral anticoagulants, and the treatment did not change the risk for a future blood clot.

“While aspirin is an incredibly important medicine, it has a less widely used role than it did a decade ago,” Barnes said. “But with each study, we are seeing that there are far fewer cases in which patients who are already on an anticoagulant are seeing benefit by adding aspirin on top of that treatment. The blood thinner they are taking is already providing some protection from clots forming.”

About Jocelyn Solis-Moreira

Jocelyn is a New York-based science journalist whose work has appeared in Discover Magazine, Health, and Live Science, among other publications. She holds a Master's of Science in Psychology with a concentration in behavioral neuroscience and a Bachelor's of Science in integrative neuroscience from Binghamton University. Jocelyn has reported on several medical and science topics ranging from coronavirus news to the latest findings in women's health.

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1 Comment

  1. Emory Kendrick says:

    No kidding. We’ve known this for decades.