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Estrogen: No Protection from Heart Disease

Estrogen treatment appears not to reduce the risk of heart attack or death from heart-related causes in healthy postmenopausal women, according to a report in the February issue of the Archives of Internal Medicine. However, some data suggest that estrogen therapy lowers coronary heart disease risk in women aged 50- 59 years.

Clinical Trials

The study was conducted by The Women's Health Initiative (WHI) and included two large clinical trials that evaluated the effect of treatment with estrogen (Premarin) on coronary heart disease risk in postmenopausal women.

The first part of the study examined the effects of estrogen plus progestin in women with intact uteri; the second part of the trial examined the effects of estrogen alone in women who had previously undergone hysterectomy.

The part of the study that involved estrogen therapy alone included a total of 10,739 women in 40 clinical centers in the US, starting in 1993. Participants were aged 50-79 years at baseline (mean age 63.6 years) who had previously undergone hysterectomy and all were randomized to receive either conjugated equine estrogens (a mix of several estrogens) 0.625 mg/day or placebo.

The researchers initially planned to study the women for 8.5 years, but the estrogen-only arm of the trial was stopped in March 2004 after only 6.8 years, because results showed that the estrogen treatment appeared to raise the risk of stroke.

Lead author Judith Hsia, MD, of George Washington University, Washington, DC, and colleagues analyzed data from the estrogen-only portion of the WHI study. During the trial, the women taking the conjugated estrogens experienced 201 coronary events, including heart attacks and deaths from cardiac causes, while among the groups of women taking placebo there were 217 events.

Overall, the risk for cardiac events or death from cardiac causes was similar between the two groups, but the data suggest that the risks may be lower in women age 50-59 years who received estrogens.

Among the 1,396 women aged 50-59 years at the start of the study who received estrogens, neither myocardial infarction (heart attack) nor coronary death was significantly reduced. However, coronary revascularization (reestablishment of blood supply to the heart) occurred less often among women taking estrogen, as did several composite endpoints, including myocardial infarction, coronary death and revascularization.

"This trial may have been unable to demonstrate a significant difference in the risk of myocardial infarction or coronary death by age group because of the low event rate in young women," the authors report.

For more information about the results of this study, visit the National Institutes of Health Women's Health Initiative website.

Conjugated Equine Estrogens and Coronary Heart Disease: The Women's Health Initiative. Judith Hsia, MD et al, Archives of Internal Medicine, volume 166, pages 357-365, February 2006.

Note: The Women's Health Initiative was funded by the National Heart, Lung and Blood Institute, National Institutes of Health, Department of Health and Human Services, Bethesda, MD. Dr. Langer received honoraria from Solvay Pharmaceuticals, Houston, and served as a consultant for Berlex, Montville, NJ, and Monarch-King Pharmaceuticals, Bristol, TN. Dr Prentice received an honorarium from Wyeth Pharmaceuticals, Madison, NJ, in 2004.

Posted: February 2006