Estrogen Found to Reduce Risk of Heart Disease
Estrogen therapy after menopause appears to cut a woman’s risk of developing coronary heart disease almost in half, according to the largest study of its kind exploring the perplexing question of the risks and benefits of hormone replacement.
The findings appear to illustrate a dramatic benefit of estrogen against the leading cause of death in older women--a benefit that researchers said should be weighed against the smaller cancer risk that may be associated with estrogen replacement.
“The bottom line is that people should pay more attention to the cardio-protection afforded by estrogen,” said Dr. Meir Stampfer, an author of the study. “. . . When you have a therapy that can reduce your risk by 45%, it can have an enormous public health impact.”
The study by researchers at Harvard Medical School and Brigham and Women’s Hospital in Boston, published today in the New England Journal of Medicine, comes as growing numbers of women are struggling to balance the proven benefits with the unsettling risks of hormone replacement.
Estrogen is prescribed initially to millions of U.S. women to minimize symptoms of menopause, such as hot flashes, sweating and other physical changes that result when production of estrogen in the ovaries slows down during and after menopause.
In addition, longer-term use can reduce the rate of bone loss and the risk of hip fractures in women. However, estrogen is also associated with a sixfold increase in a woman’s risk of endometrial cancer and, possibly, a slightly increased risk of breast cancer.
Its effects on cardiovascular disease have remained somewhat murky. Earlier studies produced contradictory results and researchers have yet to conduct the kind of definitive trial of carefully matched groups that could provide unequivocal answers.
“It is disappointing that we in medicine collectively have not made more progress toward resolving the clinical conundrum of post-menopausal estrogen replacement,” wrote Dr. Lee Goldman and Dr. Anna N.A. Tosteson in an editorial accompanying the findings.
Nevertheless, the results are based on the largest and most comprehensive study yet on hormone replacement and cardiovascular disease and they offer the most reliable evidence to date on how estrogen can reduce heart disease risk.
The results come from a study of women’s health involving 122,000 nurses. In this part of the study, the researchers followed 48,470 post-menopausal women 30 to 63 years old. Some never took estrogen, others took it and stopped, and still others continued to take it.
After 10 years of follow-up, from 1976 to 1986, the researchers found that the women who had never taken estrogen were nearly twice as likely to develop major coronary heart disease as were the women who had continued to take estrogen.
Women who had stopped using estrogen were only slightly less likely than non-users to develop major coronary disease. The researchers found no significant differences in rates of stroke among the three groups.
The study examined use of estrogen alone. Many women in the United States take progestin along with estrogen in an attempt to reduce the risk of endometrial cancer. Several researchers said they believed that the combination of the two hormones would have the same effect on heart disease as estrogen alone.
“This impact is far greater than the other impacts of estrogen on health--namely, the increase in risk of endometrial cancer and the suspected potential for increasing breast cancer risk,” said Stampfer, an associate physician at Brigham and Women’s Hospital.
“I think (the study) should settle a lot of the skepticism that still exists,” said Dr. Roger Lobo, chief of the division of reproductive endocrinology at USC’s School of Medicine. “. . . Heart disease is the No. 1 killer in women. It’s not cancer.”
Others, however, said there can be no absolute certainty about estrogen and heart disease until a randomized, controlled study is done comparing large numbers of carefully selected, similar women who take estrogen with those who do not.
In an epidemiological study such as Stampfer’s, it is possible that the women who took estrogen were fundamentally different from the women who did not in ways that the researchers were unable to recognize and account for statistically.
The National Institutes of Health intends to begin recruiting about 25,000 women for a randomized study in about a year. But Dr. William R. Harlan, head of the study, said it is likely to take another six years to arrive at definitive results.
“For the next decade, there is no free lunch,” said Cindy Pearson of the National Women’s Health Network in Washington, D.C.
”. . . Women are not going to be able to be sure that a recommendation to take estrogen to prevent heart disease is really based on firm evidence,” Pearson said.
In the meantime, experts recommend that women contemplating estrogen replacement therapy discuss it with their doctors so they can take into account risk factors, such as a family history of breast cancer, that might affect their decision.
A woman with a family history of breast cancer and no risk factors for heart disease might choose to forgo estrogen replacement, while a woman at high risk for osteoporosis or heart disease might decide to take it, physicians said.
“I think this is the most complex medical issue for a preventive maneuver that there is in the general population,” Stampfer said. “Almost all other things are so simple--quit smoking, lose weight, exercise--there’s no problem.
“But here, we’re talking about something that is known to cause cancer. And we’re saying, ‘A lot of women will benefit from this.’ So it’s a real down-home issue and every woman is either facing it now or will face it some time soon.”
