Ask the Doctors by Eve Glazier, M.D. and Elizabeth Ko, M.D

Taking Aspirin May Decrease Chances of Heart Attack

Dear Doctor: If you don't have risk factors for having a heart attack, should you be taking aspirin every day?

Dear Reader: Let's consider the risk factors, how aspirin works and the numbers. The risk factors for having a heart attack include diabetes, high blood pressure, smoking, high LDL cholesterol (the so-called "bad" cholesterol) and age.

Aspirin decreases blood clotting within the vascular system by not allowing platelets to adhere to each other. This effect can be shown even with low-dose, or 81-milligram, aspirin, also known as baby aspirin. Daily use of standard aspirin has been shown to significantly benefit those who are having a heart attack and those who have had a heart attack in the past. For people who have a history of heart attacks, taking a low-dose aspirin will decrease the chance of having another heart attack by 20 percent.

However, if you're a 40-year-old who has never had a heart attack and has none of the above risk factors, your chance of having a heart attack is low. For you, aspirin will have little benefit, and may cause more harm due to increased chances of bleeding in the stomach and a small increased risk of bleeding in the brain.

If you're a 55-year-old who has good blood pressure, low cholesterol and does not have a significant smoking history, your risk is also low, so again there is little benefit to aspirin compared to its risk.

If you're 65 without risk factors, aspirin might reduce the risk of a heart attack, but that risk reduction is offset by the increased risk of bleeding in the stomach. The same is true for a 75-year-old. These gastric bleeds that happen with aspirin use can be severe and can lead to a need for blood transfusions. They can even cause death.

If further risk factors beside age are added, then the benefits of aspirin increase. So a 55-year-old with diabetes who smokes cigarettes would clearly benefit by taking a daily baby aspirin. This benefit outweighs the risk of a stomach bleed and the risk of bleeding in the brain.

More interesting -- for some people, anyway -- is that much of the mortality benefit seen with long-term aspirin use may be in decreasing colon cancer, not in its reduction of heart attack. People who take low-dose aspirin for more than 10 years can reduce the risk of colon cancer by 20 to 40 percent, studies have shown. In fact, the mortality benefits associated with aspirin -- in the general population -- may be more strongly linked to a decrease in colon cancer than to a decrease in heart attacks.

The bottom line: If you have low risk for a heart attack or have no family history of colon cancer, aspirin offers little benefit.

(Robert Ashley, M.D., is an internist and assistant professor of medicine at the University of California, Los Angeles.)

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