To aspirin or not to aspirin
That is the question
Whether ‘tis nobler in the mind to suffer
The slings and arrows of cardiovascular disease
Or to take meds against a sea of troubles
And by opposing end them.
Unlike Shakespeare, medical recommendations are not timeless. A medication may presently be prescribed for a given condition, but if new information comes out casting doubt on it’s effectiveness, then it may fall out of favor. The use of aspirin in the primary prevention of heart disease is the latest example of this, as reported by a new US government document.
Aspirin’s anti-inflammatory and blood thinning properties are well suited for preventing heart disease. Aspirin thins the blood due to its effect on platelets. Platelets are cells which circulate in the bloodstream. If there is a tear in the wall of a blood vessel (a cut) or if a cholesterol-laden plaque in an artery breaks open, the platelets rush to the site of the injury and initiate the body’s blood-clotting mechanism. The resulting clot prevents bleeding from a cut or produces a clot within a heart artery, stopping the flow of blood and causing a heart attack. Aspirin inhibits the platelet’s ability to form a blood clot. This puts the person taking aspirin at risk for bleeding (since the platelets cannot form a blood clot) and the blood is “thinned”. Aspirin may cause bleeding in the stomach, the colon or the brain.
Aspirin is a mainstay in preventing future cardiovascular events in patients who already have heart disease. This is termed secondary prevention. In a patient who already has had a heart attack, aspirin has been shown to reduce the risk of a second heart attack, stroke or death by 33%. In secondary prevention, the enormous benefit of aspirin in reducing the risk of a second event overwhelms the small increase in the risk for bleeding. Aspirin’s role in secondary prevention is not controversial and well established.
Primary prevention attempts to prevent a heart attack or cardiovascular event in a patient who does not already have heart disease. Aspirin’s role in primary prevention is less well established and quite controversial. The issue in primary prevention is that aspirin lowers the risk for cardiovascular events by a little bit and raises the risk for bleeding a little bit with the bleeding risk outweighing the benefit (for the record, aspirin provides a 0.41% reduction in heart events but a 0.47% increase in bleeding). Whether to start aspirin in primary prevention is based on age, risk for heart disease and the risk for bleeding. In 2016, the US Preventive Services Task Force (USPSTF) recommended a low dose (81 mg) aspirin for adults aged 50 to 69 years old, who have a 10% or greater risk for cardiovascular disease (based on the American College of Cardiology cardiovascular risk calculator: http://tools.acc.org/ascvd-risk-estimator/), are not at increased risk for bleeding, and have a life expectancy of at least 10 years. In 2017, several large primary prevention studies looked at patients over the age of 60. These trials were consistent in showing that aspirin provided minimal benefit but had significant bleeding risks. Therefore, initiating aspirin for those over 70 years old for primary prevention was discouraged.
In October 2021 the USPSTF updated their recommendations based on a review of 13 new trials, encompassing 161,000 patients. They found that using aspirin for primary prevention:
1) lowered the risk for heart attack or stroke but not cardiovascular death or all cause deaths
2) increased the risk for gastrointestinal bleeding by 58% and bleeding into the brain by 31% compared to non-aspirin users.
3) low dose aspirin (81 mg) didn’t lower the risk for brain bleeding compared to higher doses.
They concluded that aspirin use for primary prevention had a small benefit for people aged 40 to 59 years old with 10% or greater 10-year risk. There is no benefit for persons 60 years or older. Lastly, the USPSTF saw no benefit for continuing aspirin for primary prevention in patients older than 75 years.
After the release of the recommendations, the news media reporting left many people confused about whether to take aspirin. In an effort to clarify whether to take aspirin, consider the following scenarios. Realize that startingaspirin is different from continuingaspirin. The USPSTF’s recommendations are for initiating aspirin. So, if you are currently taking aspirin for secondary prevention, for any of the conditions listed below, DO NOT STOP ASPIRIN.
Heart attack
Heart stent
Bypass surgery
Stroke or mini stroke (TIA)
Stable angina (blockage in the heart arteries)
If you are taking aspirin for any of the following conditions, DO NOT STOP ASPIRIN.
Plaque in the neck (carotid) arteries, aorta or leg arteries
Congestive heart failure
Atrial fibrillation
Valve surgery (especially TAVR)
Elevated coronary calcium score
If you are taking aspirin for primary prevention, DO NOT STOP ASPIRIN. It would be beneficial to talk with your doctor about the pros and cons of continuing to take aspirin. If you are considering starting aspirin to prevent a heart attack or stroke, realize that the benefit is only for younger, high-risk patients. For the vast majority of patients, starting aspirin in the absence of any of the conditions noted above is not beneficial.
So, farewell aspirin for primary prevention. Parting is such sweet sorrow.
