Should I Take a Daily Aspirin?

August 5th, 2012 By Steven Knope, MD

There are few topics that create more confusion among people than the question of whether or not to take an aspirin every day to prevent a heart attack.  If you do take an aspirin, what is the best dose?  Should you take a full 325 mg adult aspirin tablet or an 81 mg baby aspirin? Should you perhaps compromise and just lick an aspirin tablet every day?

The truth is that the correct answers to these questions are still evolving. As of July, 2012 there are still some unanswered questions. However, we are now in a better position to give individual patients more individualized advice, based upon their medical history and their risk factors for heart disease.

Aspirin Use in General: The first branch point in the decision to take aspirin is whether or not the person has had a history of coronary artery disease. If you have had a heart attack, suffer from angina, have had a stent placed in a coronary artery or a bypass operation, the data are very clear:  Everyone with a history of coronary artery disease should take a baby aspirin per day, unless there is a specific contraindication. This use of aspirin is called “secondary prevention,” which means its purpose is to prevent a second heart attack.  Aspirin, in this case, not only reduces subsequent heart attacks, it also reduces the risk of cardiovascular death and stroke.

Similarly, if you have had a prior stroke or TIA (transient ischemic attack, or “mini-stroke”) you should take an aspirin per day, unless a doctor has instructed you not to do so. Not all people with a history of stroke should take aspirin. For example, a person who has had a stroke from atrial fibrillation and is on Coumadin generally does not take an aspirin. However, in people with a history of TIA and stroke, aspirin does reduce the risk of a second stroke.

For those without Cardiovascular Disease: The benefit of aspirin in those people with no history of heart disease or stroke is not so clear. If you are one of the many who think, “Why not?  What can it hurt?” Read on.

Primary Prevention – Preventing a First Heart Attack: We have known for decades that aspirin use in a person at relatively low-risk of heart disease does help to prevent a first heart attack.  However, aspirin does not lower the death rate from cardiovascular disease, nor does it prevent a first stroke. In other words, aspirin does lower the risk of first non-fatal heart attacks, but it doesn’t prevent the kind of first heart attacks that kill people.

Now, if there were no downside to taking an aspirin, and it prevented even non-fatal heart attacks, aspirin would still be a good thing for everyone to do. For the reason, doctors used to advise all men over 50 to take an aspirin every day. However, aspirin also increases the risk of serious medical complications, such as bleeding into the stomach, GI tract and brain.  So when we are talking about prescribing aspirin to a person without heart disease or stroke, we have to do a risk-benefit analysis so see if, on balance, it is a good idea.

Individualizing Aspirin Recommendations: Even though most people who have never had coronary artery disease do not need to take a daily aspirin, it is clear that some of those people are at greater risk.  For example, a 40-year-old healthy, female marathon runner does not have the same risk for first heart attack as does a 55-year-old, obese male diabetic with a history of high blood pressure and high cholesterol. As for the woman in our example, I would not recommend a daily aspirin, because her risk of bleeding would far outweigh any small potential benefit from aspirin. For the man with multiple risk factors, I would seriously consider recommending aspiring, because his risk of heart disease over the next decade would be higher than his risk of bleeding.

Estimating the probability of a heart attack over the next decade: Not all cases are as straightforward as the two obvious examples I’ve given above. What can we do in questionable cases?  What can we do for people with a couple of risk factors?

Based upon data from the Framingham study, we can use a computerized formula to estimate the 10-year risk of any person suffering from a heart attack. By plugging in a person’s blood pressure, their smoking history, age, gender, cholesterol values and whether or not they are taking blood pressure medications, we can tell someone if they are low risk (generally less than 10% chance of having a heart attack over the next decade) or at moderate to high-risk.  Those at moderate to high-risk may be advised to take aspirin.

Since taking a daily aspirin for primary prevention lowers the relative risk of heart attack by about 20%, we can then estimate the absolute risk reduction of developing a first heart attack in a specific person by taking an aspirin. For anyone who is interested, I am happy to do this for you during your next visit.

Bullet Points:

  • Unless there is a contraindication, almost all people who have had a history of heart disease or stroke should take a daily aspirin.
  • In most cases, a baby aspirin (81 mg per day) is adequate.  If you have been advised to take an adult 325 mg pill by your cardiologist or neurologist (following a stent placement, surgery or stroke) continue to do so.
  • If you are very healthy and active, with a normal blood pressure, normal cholesterol and you do not smoke, the risks of bleeding outweigh the potential benefit of aspirin in preventing the first heart attack.  It will not save your life and it will not prevent a stroke.
  • If you are older with a couple of risk factors, ask me to do a risk calculation next time you are in the office.  Based upon your age, gender, cholesterol, smoking history and blood pressure, we can estimate your 10-year risk of having a heart attack and decide whether benefits of a daily aspirin outweigh the risks of bleeding.

Finally, keep the benefits of aspirin in perspective. As I’ve noted above, aspirin reduces the risk of heart attack, in general, by about 20% over 10 years. It carries a significant risk of bleeding. By contrast, studies done by Ken Cooper at the Cooper Clinic have shown that middle-age men who move from a sedentary lifestyle to an active lifestyle, and exercise regularly, reduce their all-cause mortality by 40% over just 5 years! That’s not just death due to heart disease, but death due to all causes.

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