As there is a belief that an aspirin a day can keep heart disease at bay,  so many now a days seem to  take it as a preventive measure, when many probably should not do it because though aspirin thins the blood and can help prevent blood clots that can clog blood vessels and cause strokes and heart attacks, long-term use of the drug also increases the risk of ulcers, gastrointestinal bleeding and bleeding in the brain. So, the American Heart Association now has come forward and advices  that aspirin should be used only for prevention when someone's risk for heart disease is especially high.