Aspirin – does it prevent heart attacks? Prevent cancer? Should we all be taking one a day? Or is it a dangerous medicine that ruins your stomach? It seems we get different advice every year. This article attempts to bring you up to date on the latest research on aspirin, specifically its use in preventing disease.

Aspirin is one of the oldest substances continuously used as a medication. Aspirin (in the form of willow bark) has been given as a treatment for pain since ancient times. Hippocrates and his contemporaries (circa 400 BCE) also recognized it as a fever reducer. The synthetic form of aspirin (acetylsalicylic acid) was synthesized in Germany in 1897 by the Bayer drug company. In the early 20th century Bayer Aspirin was widely used to treat pain, fever and the inflammation of rheumatic diseases. Aspirin fell out of favor when safer alternatives like acetaminophen (Tylenol) and ibuprofen (Advil) were developed. It wasn’t until the 1950s that the anti-platelet (blood thinning) properties of aspirin became known.

Aspirin is in a class of drugs called “Non-Steroidal Anti-Inflammatories” (NSAIDs). Examples of other NSAIDs are ibuprofen and naproxen. Aspirin works slightly differently than other NSAIDs though. Aspirin completely blocks the production of a chemical called prostaglandin. Blocking prostaglandin is how aspirin confers its benefits (relieving pain, reducing fever, decreasing inflammation and thinning blood) but also how it causes harm (inflaming the stomach lining resulting in ulcers, thinning blood enough to cause excessive bleeding).

Currently, aspirin is widely used because of its anti-platelet activity, which can prevent clot formation. When it was recognized that most heart attacks and strokes involve a clot that blocks blood flow to the heart or brain, medications that could prevent (and/or reverse) clotting were sought after (aspirin does both).

An exciting new development in the long history of aspirin is the recent observation that people who regularly take aspirin develop less, and die less, from cancer of all types, especially colorectal cancer. The mechanism by which aspirin delays cancer may also have been discovered.

What does this all mean? Should I take an aspirin every day?

The decision whether or not to take a daily aspirin needs to be individualized. The calculation involves balancing your own personal risks against the known risks and benefits of aspirin. The easiest and most clear cut area where taking a daily aspirin is beneficial is if you have already had a heart attack or stroke. This is called “secondary prevention” since the goal is to prevent a second cardiovascular event. Once you have had a heart attack or stroke taking a daily aspirin is clearly beneficial. The risk of having another heart attack or stroke is so high the anti-clotting benefit of aspirin greatly outweighs the excessive bleeding risks. It is also a fairly easy calculation if you have already had colorectal cancer or have a very strong family risk of colorectal cancer. Again in this case, the protective benefits of daily aspirin outweigh its risks.

The difficult (and controversial) calculations regarding daily aspirin come when you are a person without heart disease, have never had a stroke nor colorectal cancer (this is “primary prevention”). Can a daily aspirin prevent your first heart attack or stroke without causing harm? The U.S. Preventive Services Task Force (USPSTF) has researched and published evidence based guidelines for using aspirin for the primary prevention of cardiovascular disease.

What the evidence points to is that a daily low dose (75-81 mg) aspirin helps prevent heart attacks in some men between the ages of 45 and 80 and helps prevent strokes in some women between the ages of 55 and 80. It is only beneficial though if your personal risk of heart attack or stroke is greater than your risk of excessive bleeding. The USPSTF has links to personal risk calculators, and your GreenField Clinician can also help estimate your risks.

While these aspirin calculations are complicated, they are worth doing. Heart attacks and strokes are very common (causing 1 out of every 3 deaths in the U.S. each year) and a recent report by the Centers for Disease Control and Prevention estimates that at least 200,000 deaths from heart attack and stroke could be prevented each year in the U.S., most among people under the age of 65. Prevention of these deaths requires many actions not just adding a daily aspirin (actions such as lowering cholesterol, lowering blood pressure, quitting smoking) but a daily aspirin could help decrease these unnecessary deaths.

Unfortunately, for the primary prevention of cancer there are no guidelines for daily aspirin use yet. This is because the evidence is unclear, and the benefits have not been quantified, so it is not yet possible to do an individualized risk/benefit analysis.

So, if you are a man between the ages of 45 and 80 or a woman between the ages of 55 and 80, and you haven’t already had the aspirin discussion with your GreenField Clinician, ask to do so the next time you’re in. And, we strongly recommend that you don’t start (or stop) a daily aspirin regimen without consulting your GreenField Clinician first.