- One in four adults over 40 take a daily aspirin to prevent heart disease, despite guidelines suggesting not to.
- Contrary to popular belief, in patients with no history of heart attack of stroke the benefit from aspirin is quite small and largely offset by bleeding risk.
- The most recent 2019 guidelines from the American College of Cardiology recommend against routine aspirin use in patients over the age of 70 without heart disease or those at increased risk of bleeding.
A substantial number of people take aspirin for its heart protective benefit, even if they shouldn’t. The results of the 2017 National Health Interview Survey show that nearly one in four adults over 40 took aspirin to prevent heart disease. When you looked at adults over 70, nearly half did so. A substantial number also took aspirin on their own authority, without their physician’s advice and possibly without their knowledge as well. Mostly likely these people were listening to the oft repeated saying that everyone over the age of 50 should take a baby aspirin once a day. Where this saying comes from is not entirely clear since the problem is that aspirin for primary prevention does not seem to be terribly helpful. Although the use of aspirin after a heart attack (what we term secondary prevention) has a very clear benefit, giving aspirin to patients before they have a heart attack (what we term primary prevention) is not as clear-cut.
The history of aspirin in cardiovascular disease only dates back to 1988 with the ISIS-2 study showing that giving patients aspirin after a heart attack improved survival. Subsequent studies, and a large meta-analysis by the Antithrombotic Trialists Collaboration, showed that aspirin prevented recurrent events and established it as the standard of care. Though even back then, some studies were equivocal about whether aspirin was beneficial for patients without heart disease. Subsequent studies have been variable, although some did show a reduction in non-fatal events though no reduction in mortality. A meta-analysis on the subject found that the reduction in serious vascular events was minimal (less than 0.1%) and largely offset by the increased risk of bleeding.
Things have changed recently, largely because of a series of studies published in the New England Journal of Medicine. The first study looked at patients with diabetes but no history of heart disease. It was largely consistent with the existing data and found that while aspirin decreased the incidence of major vascular events by about 1%, this benefit was counterbalanced by a 1% increase in the risk of bleeding. The other two studies looked at patients who were aged 70 and above. These were significant studies because older patients are often underrepresented in clinical trials and there is no guarantee that what holds true at age 50 would still be valid at age 70. In the first of the two studies, daily aspirin use had no effect on preventing heart attacks and increased the risk of bleeding, although the increase was fairly minor at 2 extra bleeds per 1000 people.
The second of the two studies published in the New England of Journal of Medicine generated more headlines. Using the same patient population of patients older than 70 years, it found that daily aspirin use increased the risk of dying by about 1 per 1000 people. These excess deaths were not actually cardiac deaths but were, strangely enough, due to an excess in cancer related deaths which the authors of the paper said were “unexpected and should be interpreted with caution.”
The notion that aspirin can precipitate cancer deaths is somewhat hard to believe. There is already some pretty compelling evidence that aspirin can reduce the risk of colorectal cancer. Also just a few weeks after the papers were published, two studies came out suggesting aspirin might decrease the risk of liver cancer and ovarian cancer. It seems pretty clear that aspirin, if anything, decreases cancer risk rather than increases it.
Many people will tell you that the use of aspirin to prevent heat disease has now been “debunked.” This is not quite true since the use of aspirin in primary prevention has always been somewhat debatable and the most recent trials suggest not so much that it is unhelpful, but rather that the benefit is small and largely offset by a bleeding risk. Still, the most recent 2019 guidelines form the American College of Cardiology recommend against aspirin use for primary prevention in patients over the age of 70. This is troubling when you remember that in the National Health Interview Survey nearly half of adults over age 70 were taking a daily low dose aspirin.
Clearly, many people taking aspirin on a daily basis (by one estimate 29 million Americans and by extension probably several million Canadians) do not need to. While aspirin has great benefits for people who have had a heart attack or a stroke, its use seems to be widespread and unjustified in many people who haven’t.
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