An article from the Pak Tribune took me a bit by surprise. I've taken aspirin to prevent heart attacks for years. Now the article tells us:

In a stunning example of gender differences in medicine, a major new study found that aspirin helps healthy women avoid strokes but makes no difference in their risk of heart attacks unless they're 65 or older - the polar opposite of how the drug affects men.

The article goes on to say:

The new study "raises issues about the dangers of generalization," said Dr. Paul Ridker of Harvard Medical School and Brigham and Women's Hospital in Boston, one of the researchers. "This is an issue we thought we already had an answer to."

The Agency for Healthcare Research and Quality explains a stroke this way:

A stroke occurs when blood flow to the brain is blocked, either by narrowed blood vessels or blood clots or when there is bleeding in the brain. Deprived of nutrients, brain nerve cells begin to die within a few minutes. As a result, stroke can cause vision and sensory loss, problems with walking and talking, or difficulty in thinking clearly. In many cases, the effects of stroke are irreversible.

Aspirin is a mild blood thinner, and helps to prevent blood clots.