Overall health risks exceeded benefits from use of combined estrogen plus progestin for an average 5.2-year follow-up among healthy postmenopausal US women. All-cause mortality was not affected during the trial. The risk-benefit profile found in this trial is not consistent with the requirements for a viable intervention for primary prevention of chronic diseases, and the results indicate that this regimen should not be initiated or continued for primary prevention of CHD.

IMPORTANCE Menopausal hormone therapy continues in clinical use but questions remain regarding its risks and benefits for chronic disease prevention.OBJECTIVE To report a comprehensive, integrated overview of findings from the 2 Women's Health Initiative (WHI) hormone therapy trials with extended postintervention follow-up. DESIGN, SETTING, AND PARTICIPANTSA total of 27 347 postmenopausal women aged 50 to 79 years were enrolled at 40 US centers. INTERVENTIONS Women with an intact uterus received conjugated equine estrogens (CEE; 0.625 mg/d) plus medroxyprogesterone acetate (MPA; 2.5 mg/d) (n = 8506) or placebo (n = 8102). Women with prior hysterectomy received CEE alone (0.625 mg/d) (n = 5310) or placebo (n = 5429). The intervention lasted a median of 5.6 years in CEE plus MPA trial and 7.2 years in CEE alone trial with 13 years of cumulative follow-up until September 30, 2010.MAIN OUTCOMES AND MEASURES Primary efficacy and safety outcomes were coronary heart disease (CHD) and invasive breast cancer, respectively. A global index also included stroke, pulmonary embolism, colorectal cancer, endometrial cancer, hip fracture, and death. RESULTSDuring the CEE plus MPA intervention phase, the numbers of CHD cases were 196 for CEE plus MPA vs 159 for placebo (hazard ratio [HR], 1.18; 95% CI, 0.95-1.45) and 206 vs 155, respectively, for invasive breast cancer (HR, 1.24; 95% CI, 1.01-1.53). Other risks included increased stroke, pulmonary embolism, dementia (in women aged Ն65 years), gallbladder disease, and urinary incontinence; benefits included decreased hip fractures, diabetes, and vasomotor symptoms. Most risks and benefits dissipated postintervention, although some elevation in breast cancer risk persisted during cumulative follow-up (434 cases for CEE plus MPA vs 323 for placebo; HR, 1.28 [95% CI, 1.11-1.48]). The risks and benefits were more balanced during the CEE alone intervention with 204 CHD cases for CEE alone vs 222 cases for placebo (HR, 0.94; 95% CI, 0.78-1.14) and 104 vs 135, respectively, for invasive breast cancer (HR, 0.79; 95% CI, 0.61-1.02); cumulatively, there were 168 vs 216, respectively, cases of breast cancer diagnosed (HR, 0.79; 95% CI, 0.65-0.97). Results for other outcomes were similar to CEE plus MPA. Neither regimen affected all-cause mortality. For CEE alone, younger women (aged 50-59 years) had more favorable results for all-cause mortality, myocardial infarction, and the global index (nominal P < .05 for trend by age). Absolute risks of adverse events (measured by the global index) per 10 000 women annually taking CEE plus MPA ranged from 12 excess cases for ages of 50-59 years to 38 for ages of 70-79 years; for women taking CEE alone, from 19 fewer cases for ages of 50-59 years to 51 excess cases for ages of 70-79 years. Quality-of-life outcomes had mixed results in both trials.CONCLUSIONS AND RELEVANCE Menopausal hormone therapy has a complex pattern of risks and benefits. Findings from the intervention and extended postintervention follow-up of the 2 WHI hormone therapy trials do n...

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The Women's Health Initiative Randomized Controlled Trial The Women's Health Initiative Steering Committee * E STROGEN THERAPY HAS BEEN available to postmenopausal women for more than 60 years. Proven benefits include relief of vasomotor symptoms and vaginal atrophy and prevention and treatment of osteoporosis. Observational studies primarily examining unopposed estrogen preparations have suggested a 30% to 50% reduction in coronary events, 1-3 and an 8% to 30% increase in breast cancer with extended use. 4-6 The Women's Health Initiative (WHI) clinical trials of hormone therapy were designed in 1991-1992 using the accumulated evidence available at the time. 7 Two parallel randomized, doubleblind, placebo-controlled 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 [MPA]) would reduce cardiovascular events in mostly healthy postmenopausal women. The WHI estrogen plus progestin trial was halted in July 2002 after a mean 5.2 years of follow-up because health risks exceeded benefits. 8 Coronary heart disease (CHD), stroke, and venous thromboembolic disease were all increased in women assigned to active treatment with estrogen plus progestin. Breast cancer was also increased while colorectal cancer, hip fracture, and other fractures were reduced. The lack of benefit for CHD was *Author/Steering Committee Information, Financial Disclosures, and WHI Investigators appear at the end of this article. Context Despite decades of use and considerable research, the role of estrogen alone in preventing chronic diseases in postmenopausal women remains uncertain. Objective To assess the effects on major disease incidence rates of the most commonly used postmenopausal hormone therapy in the United States. Design, Setting, and Participants A randomized, double-blind, placebocontrolled disease prevention trial (the estrogen-alone component of the Women's Health Initiative [WHI]) conducted in 40 US clinical centers beginning in 1993. Enrolled were 10739 postmenopausal women, aged 50-79 years, with prior hysterectomy, including 23% of minority race/ethnicity. Intervention Women were randomly assigned to receive either 0.625 mg/d of conjugated equine estrogen (CEE) or placebo. Main Outcome Measures The primary outcome was coronary heart disease (CHD) incidence (nonfatal myocardial infarction or CHD death). Invasive breast cancer incidence was the primary safety outcome. A global index of risks and benefits, including these primary outcomes plus stroke, pulmonary embolism (PE), colorectal cancer, hip fracture, and deaths from other causes, was used for summarizing overall effects. Results In February 2004, after reviewing data through November 30, 2003, the National Institutes of Health (NIH) decided to end the intervention phase of the trial early. Estimated hazard ratios (HRs) (95% confidence intervals [CIs]) for CEE vs placebo for the major clinical outcomes available through ...

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