heart attacks and strokes. Now, two new studies provide further guidance on what doses are most effective and which people are most likely to benefit from this preventive therapy. The first report in the Annals of Internal Medicine looked at almost 15,600 adults at risk of cardiovascular events who were taking various aspirin doses daily. It found that lower doses of the medication -- between 75 and 81 milligrams -- were as effective as higher doses. Meanwhile, higher doses (above 100 milligrams) appeared to be associated with a greater chance of internal bleeding. In other words, a baby aspirin is probably all that most people need on a daily basis.  The second report, also published in the Annals of Internal Medicine, represents the latest thinking of the U.S. Preventive Services Task Force on the use of aspirin to prevent cardiovascular disease in people without a prior history of disease. For the first time, the task force considers people's age and gender in its recommendations. In general, it says the benefits of aspirin therapy should be weighed against the risk of gastrointestinal bleeding.  In men 45 to 79 years old deemed at risk of heart attacks, aspirin use should be encouraged if bleeding risks aren't substantial; a similar recommendation applies to women 55 to 79 years old at risk of strokes. Conversely, the task force concludes that there's no reason for doctors to prescribe aspirin as a preventive cardiovascular therapy to men younger than 45 or women younger than 55.