(HealthDay News) — For women <65 years of age, taking low-dose aspirin for years lowers the risks of heart attack, stroke, and colorectal cancer by a small amount, but the benefit is countered by an increase in the risk of major gastrointestinal bleeding, according to a study published online December 4 in Heart.

The findings are based on a clinical trial of 27,939 women who were largely healthy and relatively young – about 55 years old, on average, at the start of the study. They were randomly assigned to take low-dose (100mg) aspirin or placebo pills every other day. Over the next 15 years, about 11% of the women either developed cancer, suffered a heart attack or stroke, or died of cardiovascular causes.

Women who’d taken aspirin saw a small decrease in their odds of cardiovascular disease or colorectal cancer – but at the expense of an increase in the risk of gastrointestinal bleeding, the researchers found. That expense was clear among women <65 years of age. The researchers estimate that for every 133 women on aspirin for 15 years, one would suffer a major gastrointestinal bleeding episode – serious enough to warrant a hospital stay. And one out of 29 women would have less serious problems: a stomach ulcer or slight bleeding in the digestive tract. By comparison, 709 women would have to take aspirin to prevent one case of colorectal cancer, and 371 would have to regularly take the drug to ward off one cardiovascular complication.

The picture changed, however, as women grew older. Among those ages ≥65, 29 would need to take aspirin, long term, to prevent one case of cardiovascular disease or cancer.

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