Aspirin is recommended to prevent heart attacks in men ages 45 to 79 years and strokes in women ages 55 to 79 years, according to new guidelines from the U.S. Preventive Services Task Force (USPSTF). But the benefits of aspirin in individual patients must be weighed against the risk of gastrointestinal bleeding, cautions the USPSTF in the March 17 issue of the Annals of Internal Medicine. These recommendations are based on new evidence from the Women's Health Study and a sex-specific metaanalysis, and supersede the USPSTF's 2002 guidelines, which were based on results of studies in white men. The ideal aspirin dose to prevent cardiovascular disease is unknown, but studies suggest that 75 mg per day is as effective as higher doses. Not enough data are available to recommend aspirin in people older than 80 years.