Guidelines and recommendations have moved away from routine use for primary prevention. Here’s why.
The secondary prevention of cardiovascular disease is very clear. If you’ve had a heart attack, stroke, cardiac stent, bypass surgery or have any form of pre-existing cardiovascular disease then you should probably be on Aspirin. There is a small caveat that if you are taking another blood thinner for another reason, that may supersede the need for Aspirin and combining them might unnecessarily increase your risk of bleeding. But individualized nuance aside, anyone with pre-existing heart disease should be on Aspirin, or something comparable, unless there is some specific issue like bleeding which precludes its use.
The reason for this flip-flop is probably easy to explain. People were sicker 40 years ago. People smoked more, they walked around with blood pressures of over 150, there were no good treatments for high cholesterol, and many of the medications we now use to treat diabetes didn’t exist. Basically, Aspirin was useful because very little else was available to blunt that increased cardiovascular risk.
Now, things are better. We are much better at controlling blood pressure, treating diabetes and lowering cholesterol. Not to mention that fewer people smoke these days. Which means there is less residual cardiac risk out there in the population for Aspirin to have much of an effect.
And here lies an important point: It’s not that Aspirin is ineffective at preventing cardiovascular events. It still inhibits the platelets that are responsible for the arterial blockages that cause heart attacks and strokes. But the magnitude of the benefit is too small to be meaningful, especially when you consider that it can also increase the risk of serious bleeding.
Since the guidelines changed several years ago, Aspirin use has decreased, which suggests more physicians are recommending Aspirin discontinuation. And yet with nearly a third of older adults in the U.S. still on Aspirin for primary prevention despite recommendations to the contrary, it suggests that more work on deprescribing needs to be done. But around five per cent of the population was taking Aspirin on their own without medical advice, so it would seem that many patients are still relying on echoes of old advice. We don’t often have similar large cohort studies in Canada, but these guidelines and trends tend to be common for both countries.
As with all things, Aspirin is beneficial when used by the right patients. But patients with no history of heart disease and no high risk features are the wrong patients in this case.