Should everyone take an aspirin a day?

If you are having a heart attack, chewing a full-strength aspirin tablet can be a lifesaving move. If you have heart disease, have had a heart attack or stroke, or are at very high risk for having one, taking a low-dose aspirin every day is part of a proven strategy for preventing one of these life-changers. Aspirin makes blood platelets less "sticky." This limits the formation of clots in the bloodstream, which can trigger heart attacks and strokes. But what if you are relatively healthy? Will taking aspirin help you keep heart attack, stroke, and other forms of cardiovascular disease at bay?

If taking aspirin were without side-effects and completely risk free,  it might make sense for everyone with heart disease, or just worried about it, to take it. But aspirin does have risks. Reducing blood's clotting potential can lead to hemorrhagic stroke (bleeding inside the brain). In the stomach, aspirin can cause everything from a feeling of mild heartburn to bleeding ulcers. Severe gastrointestinal bleeding can be deadly.

The benefit-risk balance

It's the balance of benefits and risks that guides who should take aspirin for primary prevention — preventing heart attack, stroke, or another manifestation of cardiovascular disease in seemingly healthy people.

Researchers from six large primary prevention trials of aspirin pooled their data and analyzed them as if they were from a single large trial. It's a legitimate technique called meta-analysis. In this relatively healthy group of 95,000 volunteers, the reduction in heart attacks and strokes in people taking aspirin was almost counterbalanced by major bleeding in the gastrointestinal system and the brain. The researchers concluded that for individuals without previously diagnosed cardiovascular disease, "aspirin is of uncertain net value."

Another meta-analysis showed only a modest overall benefit, if any, for aspirin among people with diabetes but no cardiovascular disease, and it had little impact on heart attack or stroke. When the researchers analyzed the data by sex, aspirin reduced the risk of heart attack in men but not women.

The British journal Drug and Therapeutic Bulletin also weighed in on the topic in November 2009. After reviewing and analyzing information from relevant primary prevention studies, the journal's editors concluded that the benefits and harms "may be more finely balanced than previously thought," and aspirin should not be recommended as an across-the-board option to help healthy people prevent heart attack and stroke.

Finding the tipping point

Don't take aspirin just because you've heard it can help prevent a heart attack or stroke. It can, but it can also do some damage. There's no exact tipping point at which it makes sense to start taking an aspirin a day. If you are healthy, haven't been diagnosed with heart disease or other cardiovascular disease, and don't have risk factors for them, aspirin probably isn't for you. You'll reap little benefit while exposing yourself to side effects you'd rather stay away from. The less healthy your heart and arteries, the more likely the advantages of taking aspirin will outweigh any risks.

It isn't the easiest decision to make. If you are in the gray zone, talking with your doctor could make it more black and white.