Baby aspirin seems safer and as effective as higher doses to prevent cardiovascular disease

In the aspirin-dosing study, researchers analyzed the records of nearly 16,000 patients who took part in an already completed trial studying the effects of the blood-thinner clopidogrel, sold as Plavix, combined with aspirin. All the patients had cardiovascular disease or were at risk for it.

For the aspirin analysis, patients were divided into three groups according to the dose of aspirin they took, ranging from 75 to 81 milligrams at the low end -- about the amount found in a baby aspirin -- to 100 milligrams in the middle to 162 milligrams at the high end, or the equivalent of half an adult aspirin tablet. The patients were not randomly assigned to take aspirin or a placebo.

After two years, there was no difference in the incidence of heart attack, stroke, or death among the three groups. But the low-dose group -- people who took the equivalent of a baby aspirin -- were less likely to have bleeding.

"Daily aspirin doses of 100 milligrams or greater are not associated with clear benefit and may cause harm," the authors write. "Daily aspirin doses of 75 to 81 milligrams may provide the optimal balance between efficacy and safety in patients with known cardiovascular events or those who are at risk."

Based on a review of this and other studies showing aspirin cuts down on heart attacks in high-risk men from 45 to 79 years old and reduces strokes in high-risk women 55 to 79 years old, the US Preventive Services Task Force has issued revised recommendations. Men and women in these age groups should take aspirin if their risk factors -- diabetes, high blood pressure, and others -- make heart attacks or stroke more of a danger than bleeding in the digestive tract.

This goes further than the agency's 2002 guidance, which said that patients should consult their doctors about what might be best for them.

Taking aspirin under age 45 for men or under 55 for women is not advised, the task force statement says. Benefits are unclear for people over 80, the task force concluded.

"Using aspirin for the primary prevention of cardiovascular disease events increases the risk for major bleeding events in men and women," the recommendation says. "Aspirin use for the primary prevention of cardiovascular disease provides more benefits than harms in men or women whose risk for myocardial infarction or ischemic stroke, respectively, is high enough to outweigh the risk for gastrointestinal hemorrhage."

For people who don't fall into a high-risk category, talking to their doctors is still a good idea, said Bhatt, who was not involved in the task force recommendation.

"I actually don't think it's a great idea for people to just start taking aspirin without consulting a physician," he said. "It might seem like it's just an over-the-counter medicine. But it's just as important [to discuss] as prescription medicine."