The American Heart Association is advising that hormone replacement therapy, prescribed to more than 17 million women in the United States each year, not be used for the sole purpose of preventing heart attacks and strokes.
The recommendations are part of a statement published in the July 24 issue of the AHA's journal Circulation.
For decades, the prevailing wisdom in medicine has been that hormone replacement therapy, a daily supplement of estrogen and progesterone after menopause, is good for a woman's heart. The hormones have been shown to raise levels of good cholesterol and reduce those of bad cholesterol. Some observational studies have also suggested a statistical link between hormone therapy and lower rates of heart attacks.
However, over the last few years new research has cast doubts on the effectiveness of hormone treatment in preventing heart disease. In the Heart and Estrogen/Progestin Replacement Study, a large-scale clinical study of postmenopausal women with cardiovascular disease, researchers found that after four years there was no difference in the number of heart attacks between hormone users and non-hormone users. In fact, during the first year, there was actually a slight increase in the risk of heart attack and blood clot among hormone users.
"It could be that the effect of hormone replacement therapy to increase blood clotting outweighs the potential benefit it has," says Dr. Rose Marie Robertson of Vanderbilt University Medical Center.
In addition to blood clotting, hormone replacement therapy can also cause the inflammation of blood vessels.
Some of the conflicting results may be attributed to the lack of randomized clinical trials of hormone replacement therapy.
Dr. Lori Mosca, director of preventive cardiology at New York Presbyterian Hospital and the statement's lead author, says, "It's really only in recent years that hormone replacement therapy has been put to a real test, a true scientific study where women are randomly assigned to hormone replacement therapy or a placebo."
The new recommendations say that women who've been taking hormones for years without any problems do not need to stop. However, women should not start hormone therapy just to treat cardiovascular disease.
Instead, the guidelines suggest using hormone replacement therapy to treat common post-menopausal symptoms such as hot flashes and insomnia, and to reduce the risk of brittle bones — in short, for the proven benefits of hormone replacement.
As for preventing cardiovascular disease, the AHA suggests lifestyle changes: avoiding smoking, eating healthy, and exercising regularly.
— ABCNEWS' John McKenzie contributed to this report.