Clinical trials report
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A Randomized Trial of Low-dose Aspirin in the Primary Prevention of Cardiovascular Disease in Women Ridker PM, Cook NR, Lee IM, et al.: A randomized trial of low-dose aspirin in the primary prevention of cardiovascular disease in women. N Engl J Med 2005, 352:1293–1304. Rating: •Of importance. Introduction: Large clinical trials have shown that low doses of aspirin reduce the risk of a first myocardial infarction in men, with no effect on stroke. Similar data have not been available for women. Aims: The Women’s Health Study was a prospective randomized trial of low doses of aspirin for the prevention of a first major cardiovascular event. A cardiovascular event was defined as a nonfatal myocardial infarction, nonfatal stroke, or death due to any cardiovascular cause. Methods: The Women’s Health Study randomly assigned 39,876 women aged 45 years and older who had no history of cardiovascular disease to either 100 mg of aspirin every other day or placebo. On alternate days, participants took either vitamin E and beta carotene or placebo. Results: Over the 10-year period, the investigators did not find that aspirin reduced the risk of first-time cardiovascular events in women. At completion of the trial, 999 women had cardiovascular events, of which 522 were in the placebo group and 477 were in the treatment group. Subgroup analysis of the women over the age of 65 showed a 26% reduction in myocardial infarction. Women in this age group represented 10% of the study population. A prespecified secondary endpoint of stroke showed that low doses of aspirin reduced the risk of stroke in women by 17%. The investigators also found a 22% risk of transient ischemic attack. The rate of gastrointestinal bleeding and peptic ulcers was higher in the aspirin group. The risk of hemorrhage requiring transfusion in the aspirin group increased by 40%. Discussion: Unlike primary prevention studies in men that show a 32% risk reduction for a first myocardial infarction, low doses of aspirin did not reduce first myocardial infarctions in women. Studies in men did not show reduction in stroke risk with low-dose aspirin therapy, but
studies did find benefit for women on secondary analysis. The subgroup of women aged over 65 years benefited from aspirin prophylaxis. In secondary analysis, aspirin reduced the risk of first stroke by 17% and transient ischemic attack by 22% in these women. The stroke data was reproduced when data from randomized trials that included women were analyzed. The ratio of strokes to myocardial infarctions was 1.4 to 1 in the placebo group. Although stroke was a secondary endpoint, the risk was reduced for transient ischemic attack, and stroke rates were higher than myocardial infarction rates, suggesting more than a causal finding. Secondary analysis showed that smoking was the only risk factor to modify the cardioprotective benefit of aspirin, and the use or nonuse of hormone therapy or global cardiovascular risk influenced the aspirin therapy.
Editor’s comments Cardiovascular disease is the leading cause of death
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