These results suggest that women who already have heart disease "should not use estrogen replacement with an expectation of cardiovascular benefit," Herrington and colleagues wrote. Not everyone agrees with the team's conclusions.
The women in the study began hormone replacement an average of 23 years after their periods stopped. Estrogen "may not protect against secondary events when initiated so long after menopause," Elizabeth G. Nabel, M.D., of the National Heart, Lung, and Blood Institute in Bethesda, Md., wrote in an editorial accompanying Herrington's report.
Also, estrogen may "alter the biology of the vessel wall" in ways that lower the risk of having a heart attack but don't show up on an angiogram, she wrote. However, in another large study of women with heart disease, the participants assigned to take estrogen were more likely than placebo recipients to have a heart attack soon after beginning the study, researchers reported in the March 3, 1999, Journal of the American Medical Association. And, the estrogen didn't help with their atherosclerosis.
Even in the Women's Health Initiative, a large, ongoing trial of women free of heart disease, the participants assigned to estrogen were having slightly more heart attacks, strokes and blood clots during the first two years of the study than were placebo recipients.
Herrington and other doctors still think estrogen may help healthy women's hearts stay healthy. "There's reason to be hopeful that that may be true," said Herrington.
Reason for Optimism?
Estrogen looks like a likely crusader for the heart because taking it improves cholesterol scores. It also improves the relationship between "good" HDL cholesterol and "bad" LDL cholesterol, lowers blood pressure, increases the body's sensitivity to insulin, boosts the functioning of cells that line arteries, and increases blood flow to the heart, studies show.
Also, it appears to be estrogen that protects premenopausal women from heart attacks at the time men, who produce only a small amount of estrogen, begin to have their hearts fail. As women reach menopause, around age 51, however, their estrogen levels crash and their rate of heart attacks soar — matching men's by the time women are 65.
Another big reason doctors have viewed estrogen as the heart's superwoman: Healthy women, with no predisposing cardiovascular problems, who take estrogen are much less likely than nonusers to have heart attacks, about 30 observational studies have shown.