Aspirin may not be as effective at warding off heart attacks after all.
A new study presented by Japanese researchers at the American Heart Association conference in Chicago and published in The Journal of the American Medical Association suggests taking a low-dose aspirin every day may not help older people prevent an impending first heart attack or stroke.
Dubbed the Japanese Primary Prevent Project, the study followed the effects of aspirin therapy in 14,464 patients aged 65 to 80 who were randomly assigned by doctors to take 100 mg of enteric-coated aspirin every day or none at all. Patients were considered at high risk for cardiovascular events and needed primary prevention due to hypertension, diabetes or dyslipidemia.
They were followed for more than five years before the Data Monitoring Committee, an independent review board, cut the study short because of the lack of statistical difference in the number of heart attacks or strokes in both the aspirin and non-aspirin groups. Fifty-six members of both groups died as a result of cardiovascular events. Another 137 patients on aspirin therapy had non-fatal heart attacks or strokes during the study period, as opposed to the 151 patients who were not taking aspirin.
The researchers also took into account other factors, including hypertension, diabetes, dyslipidemia, sex, weight, age, smoking and family history of heart disease and found the results consistent among all subgroups. The researchers believe that allowing the study to run its course would have led to positive results, but not as significantly as generally believed.
"Even if the result had become statistically significant through prolongation of the study, the clinical importance of aspirin in the primary prevention of cardiovascular events would have been less than originally assumed," says Yasuo Ikeda, M.D. of Tokyo's Waseda University. "Therefore, it appears that aspirin is unlikely to show a clinically important benefit in the overall population included in this study."
The research does show that aspirin has significant benefits in reducing non-fatal myocardial infarctions by 47 percent and transient ischemic attack by 43 percent, and people who did not take aspirin were more likely to experience angina or chest pains. There is a trade-off, however, as aspirin also increases internal bleeding requiring transfusion or hospitalization by 85 percent.
In a separate editorial, Michael Gaziano, M.D., M.P.H of the Division of Aging in Brigham and Women's Hospital in Boston and Philip Greenland, M.D. of Chicago's Northwestern University write that it is likely that some people may still benefit from low-dose aspirin therapy, such as people with multiple risk factors and people who have experienced their first cardiovascular events.
"Decision-making involves an assessment of individual risk-to-benefit that should be discussed between clinician and patient," they write. "However, at present the choice of aspirin remains clear in several situations. Aspirin is indicated for patients at high short-term risk due to an acute vascular event and those undergoing certain vascular procedures; patients with any evidence of vascular disease should be given daily aspiring."
"On the other hand, patients at very low risk of vascular events should not take aspirin for prevention of vascular events, even at low dose," the doctors conclude.
