Aspirin can be your heart's best friend because it helps prevent the formation of blood clots that can cause heart attacks. Regularly taking a low-dose aspirin (81 milligrams) cuts the risk of such attacks by about 25 to 30 percent. And chewing a standard aspirin tablet at the first sign of chest pain can stop an impending heart attack by preventing blood clots from growing larger. Aspirin's anti-clotting effect also protects against ischemic stroke, the most common kind.

Moreover, research has linked aspirin to a reduced risk of Alzheimer's disease, certain cancers, type 2 diabetes, an enlarged prostate gland in men, and other health problems. No wonder, then, that more than 50 million Americans-36 percent of adults-take aspirin regularly as a preventive measure. And even more could benefit from the therapy. Some 20 percent of women and 14 percent of men who are good candidates for aspirin therapy aren't taking the drug, according to a recent study of about 1,900 people 40 and older published in the Journal of General Internal Medicine.

But aspirin's benefits have to be balanced against its risks. It can irritate the stomach and cause potentially dangerous internal bleeding, including, in rare cases, in the brain. That can lead to hemorrhagic stroke, the more deadly kind. In some people, aspirin can trigger asthma.
And not everyone benefits equally from its effects. Responses differ between men and women, for example. And preliminary but intriguing research suggests that many people have a trait that makes them resistant to aspirin's benefits.

The answers to the following 10 common questions about aspirin can help you decide if you're likely to benefit from it and, if you are, help you make the therapy as effective and safe as possible.

This article first appeared in the September issue of Consumer Reports On Health.