June 29, 2012
Dear Mayo Clinic:
I have heard that taking one baby aspirin every day can lower your risk of having a heart attack. Is that true?
Taking an aspirin every day may be appropriate in some cases, but not all. For some people who have a history of certain heart problems, stroke or diabetes, a daily aspirin may be useful. For others, though, taking an aspirin every day does not necessarily lower the risk of a heart attack and, in some cases, may be unsafe. Any decision to take a daily aspirin should be based on a doctor's recommendation.
Aspirin, which acts as a blood thinner, can lower the blood's ability to clot. When you bleed, the blood's clotting cascade is initiated such that platelets build up at the wound to help seal the opening in the blood vessel and stop the bleeding. Arteries that supply blood to the heart can become narrowed due to a build-up of fatty deposits — a condition known as atherosclerosis. If one of those deposits breaks down or ruptures, a blood clot can quickly form on the exposed irregular surface, block the artery and reduce blood flow to the heart, causing a heart attack. Taking a daily aspirin decreases the clumping action of platelets, making a clot less likely to form and block the blood vessel and possibly preventing a heart attack.
Extensive research has examined the effects of daily aspirin therapy. Certain people seem to benefit more from taking an aspirin a day. They include patients who have had a heart attack or stroke; those at high risk for a heart attack or stroke; those who have a stent placed in an artery that leads to the heart; and those who have chest pain, or angina resulting from coronary artery disease. Also, some people with diabetes, particularly older adults, may benefit from taking an aspirin a day.
Research has not shown clear benefits of daily aspirin therapy for people who are not in these categories. Some health organizations have recommended that certain people without a history of heart attacks take an aspirin every day. But there is controversy in the medical community about this approach.
In some people, daily aspirin therapy may be harmful. For example, taking aspirin may lead to other serious health problems for those who have a bleeding disorder or a health condition that interferes with the blood's ability to clot; for those who have an aspirin allergy; or for those who have bleeding stomach ulcers or a tendency to develop ulcers.
If your doctor recommends that you take an aspirin daily, make sure you know what dose the doctor prescribes for your situation. Aspirin doses usually range from about 81 mg daily — the baby aspirin dosage mentioned above — to about 325 milligrams — the amount in most regular-strength aspirin tablets. Higher doses of aspirin do not have a greater effect on blood thinning than these lower doses.
You should not start taking an aspirin daily before you talk to your doctor. If your doctor advises you to take a daily aspirin, it should be taken exactly as recommended.
— Brian Shapiro, M.D., Cardiovascular Diseases, Mayo Clinic, Jacksonville, Fla.