Aspirin is probably the most widely used and best known drug in the world. Yet it may be one of the most commonly misused drugs today — underutilized by those who would benefit and overused by those who are unlikely to benefit. To understand who will benefit the most from its use, let’s first explore the evolution of aspirin in medicine and how the drug works to prevent strokes and heart attacks.
A History Lesson
Aspirin is one of the oldest medications and was used as far back as ancient Egypt, where use of willow tree bark was recorded as an anti-inflammatory and pain reliever. The compound within the willow bark that provided these benefits was not isolated until the early 1800s in Germany and was initially named salicin. Later it came to be known as salicylic acid. Modern-day aspirin (acetylsalicylic acid) was synthesized and patented by the German pharmaceutical company Bayer in 1899, which gave it the name aspirin. It was initially marketed as a painkiller, and by 1950, it was the most frequently sold one in the world. It was not until the 1970s that studies began demonstrating that it could prevent heart attacks.
[See: 17 Ways Heart Health Varies in Women and Men.]
Clot-Busting Actions
To understand how aspirin prevents strokes and heart attacks, we have to look at the mechanism of these diseases. The precursor to heart attacks and strokes is the buildup of fatty plaques in blood vessels (arteries) that supply blood to the heart and brain. This fatty buildup in the arteries is usually caused by high cholesterol in the blood, but family genetics, smoking and other risk factors can also play a large role. Typically, a heart attack or stroke occurs when one of these fatty plaques ruptures and dumps its contents into the blood stream, which results in an intense inflammatory reaction that causes a blood clot to form. If this blood clot blocks the entire artery, it then causes a stroke or heart attack by depriving the brain and heart tissue of vital nutrients and oxygen.
One of the main drivers of clot formation is platelet activation. Platelets are very small blood cells that help stop bleeding in a damaged blood vessel by sticking together and forming a patch. When a fatty plaque in a blood vessel ruptures, the fatty material can activate platelets, causing them to form a blood clot. This juncture is where aspirin can play a crucial role. Activated platelets produce a compound called thromboxane, which causes them to become sticky and recruits neighboring platelets to form a mesh, which ultimately becomes a blood clot. Aspirin blocks an enzyme within platelets that makes thromboxane. Thus, when taking aspirin, platelets are less sticky; this in turn can potentially prevent a large stroke or heart attack when a fatty plaque ruptures. In addition to decreasing stroke and heart attack rates, aspirin has also been shown in large studies to reduce the rates of certain cancers, particularly colon cancer.
Not All Good News
Unfortunately, aspirin doesn’t just affect platelets, and it can have unintended side effects that make the drug intolerable for some. Just because it is sold over the counter doesn’t mean aspirin is safe for all patients. The most common reason for stopping aspirin is due to gastrointestinal upset and bleeding. Aspirin can degrade the protective lining of the stomach, which puts patients at risk for stomach ulcers and bleeding. The incidence of gastrointestinal bleeding is low but does increase significantly with age and even more so when aspirin is taken with nonsteroidal anti-inflammatory drugs, such as ibuprofen.
Aspirin can also be intolerable for some patients due to allergic reactions and bleeding from places other than the stomach.
[See: 8 Questions to Ask Your Doctor About Colon Cancer.]
Who Should Take Aspirin?
The question that remains is who should be prescribed aspirin? Patients can essentially be divided into two categories: those who have not yet had a stroke or heart attack, with the goal of prevention, and those who have already suffered a heart attack or stroke, with the goal to prevent another one from happening.
For this latter group, the research is fairly definitive and shows that the majority of these patients will benefit from aspirin use to prevent recurrent heart attacks and strokes. One large study, which combined the results of almost 200 smaller research studies, showed that daily aspirin use reduced the risk of future heart attack and stroke by 20 percent in patients who had already suffered one. Given this data, patients who have already suffered a stroke or heart attack should take a daily aspirin unless they have a significant intolerance.
For initial prevention in those who haven’t suffered a heart attack or stroke, the evidence is not as clear-cut. The goal of using medication for prevention is to derive more benefit (i.e., prevent a heart attack) than harm (suffer gastrointestinal bleeding or ulcer formation). Clearly, not everyone is going to have the same degree of benefit from aspirin, and in some people, the benefits will not outweigh the risks. So who may benefit the most from daily aspirin use in this group? There is no straightforward answer, but essentially people at an increased risk of heart attack and stroke may be the greater beneficiaries. Some risk factors that may qualify people for daily aspirin use include diabetes, high blood pressure, high cholesterol, tobacco use and genetics (i.e., a strong family history of stroke and heart attacks). Age and gender play a significant role, too. Those who are older or male are at increased risk for heart attack and stroke.
There are several calculators to help doctors estimate the risk of stroke, heart attack or death using these traditionally established risk factors. The most recent one recommended for adults ages 40 to 79 in the United States was published by the American Heart Association/American College of Cardiology in 2013.
Earlier this year, the US Preventive Services Task Force released new guidelines on aspirin use for primary prevention of cardiovascular disease and colorectal cancer. New to the guidelines is the cardiovascular risk calculator that aids in deciding whether to start aspirin or not. The task force generally recommends starting aspirin in adults 50 to 59 years old with a greater than 10 percent chance of developing cardiovascular disease within10 years in those people not at an increased risk for complications. In adults 60 to 69 with a greater than 10 percent chance of developing cardiovascular disease within 10 years, the decision to start aspirin should be a discussion between patients and their doctors. For adults younger than 50 or who are 70 or older, the task force found insufficient evidence to make a recommendation for or against aspirin use for cardiovascular disease and colorectal cancer prevention.
[See: The 12 Best Diets for Your Heart.]
Our Advice
Personally, we think all decisions on whether to start an aspirin regimen should be discussed by patients and their doctors to seriously consider the benefits and risks. It’s a balancing act. The patients who are most likely to benefit from starting aspirin are those who are at high risk of having a heart attack or stroke, such as patients who may have diabetes, high blood pressure or high cholesterol; are smokers; or have a strong family history of heart attacks and are at low risk for bleeding. Comparatively, young, healthy adults without the above-mentioned risk factors are unlikely to benefit from aspirin and should not start taking it.
Just last month, researchers at Brigham and Women’s Hospital released the free Aspirin Guide app on iTunes to help clinicians decide which patients are candidates for aspirin by balancing potential benefits with potential harms based on an individual’s characteristics.
Sometimes, even after using the cardiovascular risk calculator, an individual’s risk for cardiovascular disease remains uncertain because the calculator doesn’t include certain unique (i.e., nontraditional) risk factors, like autoimmune disease, history of a pregnancy with pre-eclampsia, erectile dysfunction or kidney disease. In these cases, additional risk assessment tools, like measuring the coronary artery calcium score with a CT scan, might help patients and their doctors better gauge their risk to help inform the decision about whether to start aspirin or not.
If you and your doctor decide to start you on aspirin, a question that frequently comes up is how much aspirin you should be taking. Several studies have shown that a low dose of aspirin (81 milligrams) versus a full dose (325 milligrams) is just as effective in preventing strokes and heart attacks with less risk of gastrointestinal upset and bleeding. Thus, most people should only be taking a low dose.
Aspirin can reduce the risk of strokes, heart attacks and certain cancers at the expense of increased risks for gastrointestinal upset and bleeding. If you have any of the risk factors mentioned earlier and are over 50, you should have a discussion with your doctor about aspirin to determine if taking it daily is right for you.
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Aspirin for Cardiovascular Disease Prevention: Balancing Benefits With Risks to Determine if Aspirin Is Right for You originally appeared on usnews.com
