Estrogen therapy has been available to postmenopausal women for more than 60 years, according to background information in the article. Despite decades of use and considerable research, the role of estrogen alone in preventing chronic diseases in postmenopausal women remains uncertain.
The Women's Health Initiative (WHI) clinical trials of hormone therapy were undertaken to determine whether conjugated equine estrogen (CEE) alone (for women with prior hysterectomy) or in combination with progestin (medroxyprogesterone acetate) would reduce coronary heart disease (CHD) events in mostly healthy postmenopausal women. The WHI estrogen plus progestin trial was halted in July 2002 because health risks exceeded benefits, including increased risks for CHD, stroke and breast cancer.
In this new report on the estrogen alone intervention, the WHI investigators assessed the effects of CEE, the most commonly used postmenopausal hormone therapy in the U.S., on major disease incidence rates. In this randomized, double-blind, placebo-controlled disease prevention trial conducted in 40 U.S. clinical centers beginning in 1993, 10,739 postmenopausal women, aged 50-79 years, with prior hysterectomy were enrolled, including 23 percent of minority race/ethnicity. The women were randomly assigned to receive either 0.625 mg/day of CEE or placebo.
The WHI authors write that in February 2004, the National Institutes of Health (NIH) decided to end the intervention phase of the trial early. Based on data for the major clinical outcomes available through February 29, 2004, the researchers found that with an average of 6.8 years of follow-up, C
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