Women's Health Initiative Studies The Women's Health Initiative (WHI) enrolled a total of 27,000 predominantly healthy postmenopausal women to assess the risks and benefits of either the use of Premarin (0.625 mg conjugated equine estrogens per day) alone or the use of Prempro (0.625 mg conjugated equine estrogens plus 2.5 mg medroxyprogesterone acetate per day) compared to placebo in the prevention of certain chronic diseases. The primary endpoint was the incidence of coronary heart disease (CHD) (nonfatal myocardial infarction and CHD death), with invasive breast cancer as the primary adverse outcome studied. A "global index" included the earliest occurrence of CHD, invasive breast cancer, stroke, pulmonary embolism (PE), endometrial cancer, colorectal cancer, hip fracture, or death due to other cause. The study did not evaluate the effects of Premarin or Prempro on menopausal symptoms. The Premarin-only substudy is continuing and results have not been reported. The Prempro substudy was stopped early because, according to the predefined stopping rule, the increased risk of breast cancer and cardiovascular events exceeded the specified benefits included in the "global index." Results of the Prempro substudy, which included 16,608 women (average age of 63 years, range 50 to 79; 83.9% White, 6.5% Black, 5.5% Hispanic), after an average follow-up of 5.2 years are presented in Table 4 below. TABLE 4. RELATIVE AND ABSOLUTE RISK SEEN IN THE PREMPRO SUBSTUDY OF WHI a Placebo n = 8102 Prempro n = 8506 Event c Relative Risk Prempro vs Placebo at 5.2 Years (95% CI*) Absolute Risk per 10,000 Person-years CHD events 1.29 (1.02-1.63) 30 37 Non-fatal MI 1.32 (1.02-1.72) 23 30 CHD death 1.18 (0.70-1.97) 6 7 Invasive breast cancer b 1.26 (1.00-1.59) 30 38 Stroke 1.41 (1.07-1.85) 21 29 Pulmonary embolism 2.13 (1.39-3.25) 8 16 Colorectal cancer 0.63 (0.43-0.92) 16 10 Endometrial cancer 0.83 (0.47-1.47) 6 5 Hip fracture 0.66 (0.45-0.98) 15 10 Death due to causes other than the events above 0.92 (0.74-1.14) 40 37 | ||||
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