Aspirin is a very old drug but scientists are still trying to figure out if it should be used to prevent heart attacks and strokes. In April of 2016 the United States Preventive Services Task Force put out a recommendation regarding aspirin. These experts suggested that low-dose aspirin use could prevent heart attacks, strokes and colorectal cancer. The benefits were “modest” and there was a risk of bleeding. Then a study in The Lancet (July 12, 2018) analyzed data from 10 trials. The authors concluded that low-dose aspirin was ineffective for people weighing more than 154 pounds. Now a new meta-analysis published in JAMA (Jan. 22, 2019) reviewed the results of 13 placebo-controlled trials with a total of more than 160,000 participants and over 1 million participant-years. The authors found that people taking aspirin were significantly less likely to suffer heart attacks, strokes or death from cardiovascular causes.
Aspirin For Your Heart? Should You or Shouldn’t You?
We cannot answer the above question on a global basis. And each individual will need to discuss this question with her primary care provider. That said, let’s drill down on the data. The JAMA study did an excellent job in providing absolute benefit and risk data. We only wish more research was presented this way.
The absolute risk reduction with aspirin was small, just 0.4 percent. How did the researchers come up that number? Please pay careful attention. This gets complicated.
The investigators analyzed the data for primary outcomes. Primary = death from cardiovascular causes, nonfatal heart attacks and nonfatal strokes. There were 3,072 such events in the no aspirin group and 2,911 events in the aspirin-taking group. That was an 11% reduction in events. But 265 people would have needed to take aspirin to prevent one event.
Here’s another way to think of this benefit. There were 61.4 events per 10,000 participant-years in the no aspirin group. There were 57.1 events per 10,000 participant-years in the aspirin group. That was a statistically significant reduction in cardiovascular events, but as you can see, not that impressive.
How Dangerous is Aspirin for your Heart?
The analysis also considered whether people taking aspirin were more likely to experience major bleeding. They were, although here too the difference was small, about 0.5 percent. The risk and benefit were almost evenly matched.
There were 23.1 major bleeding events per 10,000 participant-years in the aspirin-taking people and 16.4 serious bleeding events per 10,000 participant-years in the no-aspirin group.
Making Decisions About Aspirin for Your Heart:
The relatively small benefits and risks make a decision to use aspirin more complicated, especially for people without heart disease. The authors note:
“Consequently, the decision to use aspirin for primary prevention may need to be made on an individual basis, accounting for the patient’s risk of bleeding and their views on the balance of risk vs benefit.”
An editorial in the same issue of JAMA notes that:
“Because weighing the risks and benefits of aspirin in primary prevention is complicated, it should involve a shared decision-making discussion between the patient and the clinician.”
The bottom line seems to be that if your risk of a serious cardiovascular event is pretty high, low-dose aspirin could be modestly beneficial. If, on the other hand, your risk of bleeding is high, then the equation shifts against aspirin. Sorry…we warned you that it’s complicated. When it comes to aspirin there are no easy answers. You can read more about the benefits and risks of aspirin here.