Medical Examiner

What’s Going On With the New Aspirin Recommendations?

A look at how aspirin has been used over the years—and where the medical advice stands today.

A side-by-side of a human heart and aspirin spilling out of a bottle.
Photo illustration by Slate. Photos by Paul Campbell/iStock/Getty Images Plus and ironstealth/iStock/Getty Images Plus.

An aspirin a day was, for decades, believed to keep heart disease at bay, and older Americans out of the doctor’s office. But proposed recommendations from the U.S. Preventive Services Task Force moved away from this piece of common wisdom last week.

Preliminary advice from the panel suggests that Americans over the age of 60 who haven’t had a heart attack or stroke should not take daily aspirin. The panel also advised that high-risk patients ages 40 to 59 who haven’t had a heart attack speak to a doctor before starting an aspirin regimen. The recommendations, which will be finalized in November at the earliest,  follow a review of medical research, revealing that the risk of internal bleeding from taking regular aspirin appears to outweigh the benefits in those groups. The directive against daily aspirin for many people might seem like a bit of a flip-flop—aspirin is good! Wait, now it’s bad! But delving into the history of aspirin’s use for heart attacks makes it clear that the shift has been a lot more gradual than that.

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Aspirin, in some form, has been used to treat pain for thousands of years. One of the earliest known instances of aspirin being recruited to prevent heart disease occurred during the 1950s, when Lawrence Craven, a California physician, noticed that children who chewed on aspirin-infused gum had bleeding complications. Craven figured that the drug’s blood thinning effects could be harnessed to ward off heart attacks. Craven asked all his healthy male patients between the ages of 45 and 65 to take a daily aspirin. Within the same decade, he published three research articles determining that aspirin warded off heart attack and stroke. (It’s been reported that Craven asked patients who’d recovered from a heart attack to take an aspirin as well.)

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Though Craven and other physicians prescribed aspirin off-label as a preventative, larger, more robust clinical investigations of aspirin’s effect on the primary prevention of cardiovascular disease didn’t begin until the 1970s and 1980s. (Primary prevention refers to medical intervention in patients at risk for a heart attack or stroke but who haven’t had one.) It was around that time that doctors also began giving aspirin as soon as they could after a heart attack. Also in the ’80s, the Food and Drug Administration issued two important authorizations for aspirin use: In 1980, aspirin was approved for preventing future strokes in folks who’d already had one, and in 1985, the same endorsement was announced for people who’d had heart attacks. During the early 1990s, the American College of Chest Physicians recommended that aspirin be used for preventing the first heart attack or stroke in people over the age of 50. And, in 1995, the Physicians’ Health Study, which began in 1982, released its findings that a low-dose aspirin did in fact decrease the risk of the first heart attack.

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Since then, the need for aspirin as a stroke and heart attack preventative has declined as medicine has gotten better at stopping them from happening in the first place. “We’re now doing a much better job of controlling blood pressure, of controlling cholesterol—maybe even, you know, to a certain extent controlling diabetes and fewer people are smoking,” said Donald Lloyd-Jones, a cardiologist and volunteer president of the American Heart Association. With those risk factors under better control, people who haven’t had a heart attack just don’t need aspirin.

“In the early 2000s, when somebody came to me and said, ‘Well, I want to reduce my risk of having a heart attack or stroke,’ aspirin would be one of the first things to discuss,” said Salim Virani, a professor at Baylor College of Medicine. “Now it is like the third or the fourth thing.”

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There’s been mixed evidence on aspirin for a while now, with some doctors arguing against recommending it for everyone in older age groups as early as 2012—like primary care doctor Michael Tam did in the Conversation. The doubt got a boost in 2018 when three large-scale clinical trials, including a total of more than 47,000 participants, solidified the idea that daily aspirin isn’t a perfectly harmless healthy habit. These studies, which looked at people who had never had a heart attack, compared aspirin takers against a group that got a placebo. Researchers tracked major cardiovascular events, as well as the number of participants who experienced major bleeding. This kind of bleeding typically occurs in the stomach or head and, in some cases, requires hospitalization or a blood transfusion, or can cause death. There are a couple ways aspirin can contribute to these events, explains Lloyd-Jones: “Aspirin can cause bleeding in the GI tract by directly irritating the lining of the stomach, or by potentiating something that is already bleeding, because aspirin slows the blood’s ability to clot.”

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One of the studies, which focused on older adults, found that, in general, using aspirin for primary prevention significantly increased the risk of major bleeding, while having minimal effect on the risk of heart disease. A second study looking at patients with diabetes concluded that aspirin was useful in preventing any serious cardiovascular complications, but it caused major bleeding. Not everyone is at the same risk of that happening. “The risk of bleeding depends on many things, like whether there is a history of bleeding [and] what other medications a patient may be taking,” says Lloyd-Jones. But the outcomes prompted the American Heart Association and the American College of Cardiology to issue their own recommendations, which Virani helped write, against the blanket use of aspirin for primary prevention in 2019.

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Aspirin isn’t inherently dangerous, but the risks need to be weighed against potential benefits. It’s important to emphasize that this proposed recommendation change focuses on primary prevention. For people who’ve had a heart attack, a stroke, a stent placed, or bypass surgery, the risk calculus changes a bit. They need more aggressive blood thinning, since they have heart disease and a higher risk of experiencing a future heart attack or stroke. In most cases, this outweighs the risk of bleeding, explained Lloyd-Jones.

While there’s always the possibility of new evidence, it would make sense if the recommendations have shifted away from aspirin-for-everyone for good. “For primary prevention, aspirin may well have run its life course,” said Lloyd-Jones. “We’re really understanding, if we take away the fuel that creates plaques in our arteries—that is what leads to heart attacks and strokes—then we don’t need the safety net of aspirin anymore.”

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