Low-Dose Aspirin Use Linked to Increased Internal Bleeding

A new survey published on June 25, 2024 in the Annals of Internal Medicine has found that tens of millions of adults aged 60 and older are unknowingly putting themselves at increased risk for internal bleeding by routinely taking low-dose aspirin. The survey results suggest that the drug’s potential risks may outweigh the drug’s potential benefits in preventing heart attacks and strokes for older adults.¹

In 2021, researchers at the Cleveland Clinic surveyed over 186,000 U.S. adults aged 40 and older about their aspirin use. Nearly 20 percent reported using aspirin for “primary prevention” to prevent a heart attack or stroke. The rate was even higher among those aged 60 and up, with almost 30 percent using aspirin for the same purpose.

Over five percent of those taking aspirin for primary prevention did so without a doctor’s advice, while the remaining 95 percent had either informed their doctors about their aspirin use or had been advised by their doctors to take it. Researchers found that in the overall group of women, aspirin did not reduce the risk of heart attacks, but it did increase the risk of bleeding. Only “some” benefit was seen for women over 65.²

Low-Dose Aspirin for Heart Attack or Stroke Prevention Dates from the 1990’s

The widely recognized guidance of some doctors to take aspirin to prevent serious medical events dates back to the 1990s when published research hypothesized that taking low-dose aspirin regularly could reduce the risk of heart attack or stroke by preventing blood clots. “Aspirin works by targeting an enzyme called cyclooxygenase,” which is essential in clot formation, Dr. Prashant Vaishnava, a preventive cardiologist at Columbia University Irving Medical Center, said in an interview. “Through that inhibition, it actually increases the risk of bleeding because it renders the platelets less likely to clump together,” a process that typically helps stop internal bleeding, he explains.²

As with all drugs prescribed by doctors, it was thought at the time that the potential benefits of proactively taking low-dose aspirin—to prevent heart attack or stroke—outweighed the risks of internal bleeding in the gastrointestinal tract. However, a 2018 study challenged this assumption, particularly for older adults. The study concluded that using low-dose aspirin to prevent heart problems in older adults led to a “significantly higher risk of major hemorrhage” and did not significantly reduce the risk of heart disease compared to the placebo group.³

“The decision to treat with any medication is essentially a balancing act between the benefits and risks of that drug,” Mohak Gupta, MD, a senior resident physician at Cleveland Clinic and co-author of the new study, said in an interview. “The benefits of primary prevention aspirin are lower and risks are higher than we previously knew.”²

Aspirin Does Not Prevent Heart Attacks in Women: 2005 Study

More troubling than the 2018 findings is a 10-year Women’s Health study from 2005 that followed 40,000 healthy women, which found that low-dose aspirin did not protect them from first heart attacks at all. In the study, half of the participants who took 100 milligrams of aspirin every other day showed no reduced likelihood of suffering heart attacks compared to the other half who took placebos. ⁴

While the study did find that low-dose aspirin modestly reduced the risk of stroke in women, the results were almost the opposite of previous trials, mostly involving men. Those studies, including the landmark Physicians’ Health Study, indicated that aspirin therapy lowers the risk of heart attack but slightly increases the risk of stroke, suggesting that men and women respond differently to aspirin. “What was really surprising and not anticipated was this gender difference,” said Elizabeth G. Nabel, MD, director of the National Heart, Lung, and Blood Institute, which helped fund the Women’s Health Study.^{5 6}

Despite the decades-old Women’s Health study, the U.S. Preventive Services Task Force (USPSTF) did not revise its guidance for aspirin use until 2022. They now suggest that adults aged 40-59 with a higher risk of cardiovascular disease make an individual decision about starting low-dose aspirin after consulting with their healthcare provider, while adults aged 60 and older are advised against beginning aspirin for primary prevention due to the increased risk of bleeding.⁷

Legal Battles and Serious Health Concerns Embroil Bayer’s Aspirin

Bayer, known for manufacturing aspirin, has been embroiled in legal challenges. In 2000, the Federal Trade Commission (FTC) charged Bayer with making unsubstantiated claims about the benefits of daily aspirin use in advertisements. The FTC cautioned that same year that regular aspirin use may carry health risks and lacks conclusive evidence for preventing strokes and heart attacks in most adults.⁸

Concerns have also since emerged about aspirin use during pregnancy, with a growing body of evidence indicating a potential link to increased risks of specific birth defects, such as amniotic band syndrome. According to a 2011 study published in the American Journal of Obstetrics and Gynecology, babies were three times as likely to be born with no eyes, or with abnormally small eyeballs that often cause blindness, if their mothers had taken aspirin or naproxen (sold under the brand name Aleve).⁹

“Over-the-Counter Does Not Mean Safe,” Cardiologist Warns

“Not only was there lack of benefit for the younger women taking aspirin, but there was also a question of harm,” says Erin Michos, MD, MHS, associate director of preventive cardiology for the Ciccarone Center for the Prevention of Heart Disease. “It’s important for people to realize that just because aspirin is over-the-counter does not mean it is necessarily safe. Many patients take aspirin because they think it’s good for their hearts, but it carries some serious risks.”¹⁰

“If you’ve had a heart attack or stroke, there’s no doubt that taking low-dose aspirin is beneficial,” Michos continues. “But if you don’t have heart disease, should you take it just in case? The answer for most individuals is probably not.” ¹⁰

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