BACKGROUND:
Various doses of aspirin have been shown to be effective in preventing thrombosis or vascular occlusion in several clinical conditions. Short-term studies have documented the efficacy of aspirin in preventing occlusion of saphenous vein bypass grants, preventing myocardial infarction in patients with unstable angina, preventing transient ischemic attacks and stroke in men with cerebral vascular disease, preventing occlusion of injured coronary arteries following transluminal angioplasty and aiding in reducing myocardial infarction and total mortality in patients receiving fibrinolytic therapy. Additionally, aspirin has been effective in the secondary prevention of myocardial infarction in subjects with known coronary artery disease. The results of the Physicians' Health Study, a large-scale primary prevention trial of aspirin in male physicians, have shown a decrease in myocardial infarction, a non-significant increase in cerebral vascular events, and no difference in overall mortality. However, few studies have addressed the efficacy of aspirin in vascular diseases in women, and it is possible that the risk to benefit ratio may be different in women. Specifically, there have been no large primary prevention trials in women, who are at risk of coronary heart disease, especially after menopause.
DESIGN NARRATIVE:
The Women's Health Study (WHS) is a randomized, double-blind, placebo-controlled trial using a 2x2 factorial design. The WHS is sponsored by both NHBLI (HL080467) and NCI (CA047988). Participants were randomly assigned to either Vitamin E (600 IU every other day) or placebo; and to aspirin (100 mg every other day) or placebo. Approximately 1.75 million female health professionals were contacted by mail to determine if they were suitable for inclusion in the study. A three-month run-in phase was performed to screen out those with poor compliance. Randomization, which began in February 1993 and ended in January 1996, was stratified on five-year age groups. The primary endpoint is the reduction of the risk of all important vascular events (a combined endpoint of nonfatal myocardial infarction, nonfatal stroke, and total cardiovascular death) and a decrease in the incidence of total malignant neoplasms of epithelial cell origin. Secondary endpoints are the individual components of the combined endpoints. Compliance is measured by replies to a questionnaire sent out every year.
The WHS has been extended through March, 2009 for additional observational follow-up of the cohort. As part of the initial trial, pre-randomization blood samples from 28,345 participants were frozen and stored for genetic analysis which has been supported by non-federal sources. The study will develop improved prediction scores for total and specific cardiovascular disease outcomes that are based not only on traditional risk factors but also on novel plasma and genetic markers. The study will also develop similar prediction scores for health conditions that are major cardiovascular disease risk factors (including type 2 diabetes, hypertension, and the metabolic syndrome) and will evaluate genotype-phenotype interactions and interactions between traditional and novel cardiovascular disease risk factors in the prediction of cardiovascular disease events. |
