The study also found that taking low-dose aspirin daily increases a patient's risk of bleeding, but the researchers said the protective benefits of aspirin outweigh this side effect. A daily dose of aspirin is considered low if it is between 81 milligrams and 325 milligrams.
"Among patients with stable cardiovascular disease, we found that low-dose aspirin reduced incidence of heart attack, stroke and death," said cardiology fellow Jeffrey Berger, M.D., who presented the results of the study on Wednesday, Nov. 15, at the annual scientific sessions of the American Heart Association, in Chicago.
"We also saw an increased risk of bleeding among patients taking aspirin, but as in the decision-making process involving any therapy, there is always the weighing of benefits and risks," Berger added. "Since a great majority of patients can tolerate aspirin, the benefits appear to outweigh the risks. Aspirin is a drug that has been used for many years. It is well-understood, effective, inexpensive and widely available. In aspirin we have a proven life-saver."
The study was supported by Duke's Division of Cardiology.
Aspirin exerts its protective effect by preventing the clumping together of platelets circulating in the blood, according to the researchers. It is this anticlotting action that also causes unwanted bleeding.
In the Duke study, Berger and colleagues combined the data from six clinical trials that enrolled patients with stable cardiovascular disease or stable angina, or chest pain, and gave them low-dose aspirin. In total, the trials included 9,853 patients.
The researchers found that patients who took low-dose aspirin had a 26 percent reduction in the risk of a nonfatal heart attack, a 25 percent reduction in the risk of stroke and a 13 percent reduction in risk of death, compared with similar heart patients who did not take aspirin. Taken together, Berger said, patients on low-dose aspirin had a 21 percent reduction in risk of experiencing a major cardiovascular event, a measurement that is the combination of the rates of nonfatal heart attack and stroke and of cardiovascular death.
In terms of aspirin's effect in promoting bleeding, the study found that one patient out of 111 who received low-dose aspirin experienced a bleeding episode, Berger said.
Putting the results another way, Berger said, the results suggest that treating 83 patients will prevent one nonfatal heart attack, treating 40 patients will prevent one stroke, treating 30 patients will prevent one major cardiovascular event and treating 71 patients will prevent one death.
"When compared to other medications that have been proven effective in preventing cardiovascular events, aspirin comes off looking very good," Berger said.
For example, 91 patients would need to be treated with ACE inhibitors to prevent one death, compared with 71 patients for aspirin, he said. ACE inhibitors dilate blood vessels, making it easier for the heart to pump blood. Ninety-one patients would need to be treated with the inhibitors to prevent one heart attack, compared with 83 for aspirin, and 167 would need to be treated with the inhibitors to prevent one stroke, compared with 40 patients with aspirin.
"These comparisons show that a cheap and inexpensive medicine like aspirin is just as good, if not better, than other expensive medicines," Berger said.
Still, there is room for improvement in aspirin therapy, he said. In particular, he said, more study is needed to identify what dosage in the low-dose range -- from 81 milligrams to 325 milligrams a day -- will provide the best benefit-to-risk profile.
Richard Merritt | EurekAlert!
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