A large-scale, 10-year study of nurses indicates that women who take the female hormone estrogen after menopause can cut their risk of heart disease in half.
Medical experts say the new findings should help answer a question that has troubled millions of middle-aged and elderly women: Are the benefits of estrogen worth the risks?
Besides its effect on heart disease, the drug averts thinning of the bones, a serious disease in the elderly. But women have been concerned by evidence that taking estrogen also can bring on cancers of the breast or of the lining of the uterus.
After analyzing the pros and cons, Dr. Lee Goldman of Brigham and Women's Hospital in Boston concluded that "the benefits of estrogen outweigh the risks, substantially."
The study is published today in the New England Journal of Medicine, accompanied by an editorial by Dr. Goldman.
In the last decade there have been some two dozen studies of how estrogen affects heart disease in women, but the results have been contradictory. The new survey, which involved 48,470 nurses, is larger than all previous studies combined, and the greater numbers yielded a clearer conclusion.
"This is a very important study," said Dr. Claude Lenfant, director of the National Heart, Lung and Blood Institute.
Dr. Antonio Gotto, chairman of the Department of Medicine at the Baylor College of Medicine in Houston, said, "The data from many of the previous studies have been very limited. The numbers are not large enough to be convincing." For that reason, he added, "This study is very important."
Dr. Gotto, past president of the American Heart Association, said he hoped the new study would be "an added impetus to both physicians and to females to intervene."
But Dr. Goldman said that while the study was convincing to most researchers, it fell short of being "debate-ending."
Instead, he said, he expected the results "will be a pendulum swinger," leading many women who were undecided about whether to take estrogen after menopause to take the hormone.
The study, directed by Dr. Meier J. Stampfer of the Brigham and Women's Hospital, followed menopausal women 30 to 65 years of age who had no history of cancer or heart disease when the study began.
After 10 years, the investigators documented 405 cases of heart attacks or deaths from heart disease. They also found that women who were taking estrogen had half as many heart attacks and cardiovascular deaths as did women who did not take the hormone.
Even when investigators limited their analysis to the women in the study who were at particularly low risk of having a heart attack, the finding stood. The researchers said that indicated that estrogen could even benefit women not considered likely to have heart disease.
It is already known that estrogen taken after menopause prevents thinning of the bones, a disease of the elderly known as osteoporosis.
The drug also slightly increases the risk of breast cancer and makes it six times more likely a woman will get cancer of the lining of the uterus.
But heart disease is the leading cause of death in women, killing more women each year than all cancers combined. Its incidence soars after menopause, when a woman's ovaries no longer supply estrogen. Researchers say the effects of estrogen in preventing heart disease completely overwhelm its propensity to cause cancer.
Dr. Goldman wrote that a woman's chance of dying from heart disease is much greater than is her risk of dying from breast cancer, from complications after a hip fracture caused by osteoporosis, or from cancer of the uterine lining.