(HealthDay News) — In healthy women, long-term use of alternate-day, low-dose aspirin may reduce the risk for colorectal cancer, according to a study published in the July 16 issue of the Annals of Internal Medicine.

Nancy R. Cook, Sc.D., from Brigham and Women’s Hospital in Boston, and colleagues analyzed observational follow-up data from 33,682 women aged 45 years or older participating in the Women’s Health Study. Women had been randomized to 100 mg of alternate-day aspirin or placebo through March 2004, with a median 10-year follow-up.

The researchers found that there were 5,071 cancer cases (including 2,070 breast, 451 colorectal, and 431 lung) and 1,391 confirmed cancer deaths. Aspirin had no association with total cancer (hazard ratio [HR], 0.97; P = 0.31) or breast (HR, 0.98; P = 0.65) or lung cancer (HR, 1.04; P = 0.67), but aspirin was associated with reduced colorectal cancer (HR, 0.80).

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This 42% risk reduction emerged after 10 years (HR, 0.58). Aspirin was not associated with reduced cancer deaths or colorectal polyps. Furthermore, there was significantly more gastrointestinal bleeding (HR, 1.14) and peptic ulcers (HR, 1.17) in the aspirin group.

“Long-term use of alternate-day, low-dose aspirin may reduce risk for colorectal cancer in healthy women,” the authors write.

The aspirin and aspirin placebo for the study were provided by Bayer HealthCare.