The report is in the Journal of the American Medical Association.
Italian researchers studied more than 370,000 patients looking for differences in how aspirin affects those with diabetes and those without. But their findings apply to millions of people hoping to prevent heart problems
Doctors have known for years that aspirin increases the risk of bleeding. But many say the study highlights the issue of calculating risks and benefits of any medical treatment, including one that may seem as harmless as taking an aspirin a day.