Harvard Men's Health Watch

Ensuring aspirin's benefit

Q. Is it true that in some people, low-dose aspirin doesn't help to prevent heart attacks? Should I take a higher dose to make sure it works?

A. Recent research suggests that the cardioprotective benefit of aspirin may vary for different people, although the reasons are unclear. Daily low-dose aspirin (81 milligrams) suppresses the body's clotting response. This helps prevent blood clots that cause heart attacks and most strokes. If you are at elevated risk because of known heart disease or a past stroke, taking a daily
aspirin can save your life.

However, aspirin does not prevent cardiovascular problems in all those at risk. This had led to speculation that some people may be "resistant" to the effects of aspirin and may need a higher dose. Research suggests that the anti-clotting effect of aspirin is weaker than expected in about one in 50 people with heart disease. But careful repeat testing revealed that most of the allegedly aspirin-resistant people were not taking the aspirin as directed. If a person takes the aspirin as directed, the aspirin resistance disappears.

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