Aspirin: A user's guide to who needs it and how much to take

Just because you can buy aspirin without a prescription (and for pennies a tablet) doesn't mean everyone should be taking it to prevent a heart attack or stroke.

You might expect that by now doctors and researchers would know everything they need to know about aspirin, a hundred-year-old drug that is taken by nearly half of Americans over age 55. But that isn't the case. Some important uncertainties still linger regarding the use of the ubiquitous white pill. Two unsettled issues are who should take aspirin to prevent a heart attack or stroke and how much to take.