It's clear that daily aspirin can be beneficial for people who have had a heart attack or an ischemic stroke. Scores of studies have shown that this simple treatment reduces the chance of having a repeat heart attack or stroke.

Might the drug also prevent first heart attacks or first strokes? A new study followed 14,000 Japanese, age 60 and older with high blood pressure, high cholesterol, or diabetes.

The results, in last month's Journal of the American Medical Association, found no overall benefit to taking an aspirin a day. But the study hardly puts the question to rest.

The study did find slightly fewer heart attacks and transient ischemic attacks (like a stroke, but ending quickly without damage) with aspirin. One reason the study failed to show an overall benefit was that the control group had few heart events. (It's hard to detect protection against a rare condition.)

Also, the study found an unacceptable rate of serious side effects in those who took aspirin. The properties that lower clotting and plaque buildup also raise bleeding risks, such as catastrophic bleeding in the brain.

The results mean doctors must be cautious giving the pill to patients who have never had heart attacks or strokes. - Washington Post