WEDNESDAY, July 11, 2007 (HealthDay News) -- Five years after the results of the Women's Health Initiative sounded the supposed death knell for hormone replacement therapy, experts gathered Wednesday to reassess those results and discuss the fine-tuning and evaluation that has taken place since.
"The science has evolved substantially in the past five years," Dr. JoAnn Manson, chief of the division of preventive medicine at Brigham and Women's Hospital in Boston, said at a press conference sponsored by the Society for Women's Health Research. "There's been mounting evidence that a woman's age and amount of time since onset of menopause may influence the effect of hormone therapy."
The Society for Women's Health Research is a nonprofit organization but has received funds from companies such as Amgen, Cytyc, Eli Lilly, Ethicon and Wyeth.
The original Women's Health Initiative (WHI) was halted when U.S. researchers found an increased risk of adverse events which, depending on whether the woman was taking estrogen alone or estrogen plus progestin, included heart attack, stroke, breast cancer and blood clots. Manson was one of the principal investigators on the WHI trial.
The average age of women enrolled in the WHI was 63, or about 12 years past menopause.
And the trial was designed not to look at how well hormone therapy combated menopausal symptoms such as hot flashes, but whether it could play a role in chronic disease prevention.
"The WHI was designed to evaluate the balance of benefits and risks of hormone therapy in generally healthy postmenopausal women when used for chronic disease prevention," Manson said. "At the time WHI was started in the early 1990s, it was becoming increasingly common in clinical practice to use hormone therapy in older women who were at high risk of cardiovascular disease, or who already had a diagnosis of cardiovascular disease, in order to prevent future cardiovascular events."
Since then, it has become increasingly clear that hormone therapy has different benefits and risks, depending on the age of the woman.
Just last week, Manson and her colleagues reported in the New England Journal of Medicine that women in their 50s who take estrogen therapy have lower levels of dangerous calcium deposits in their arteries, suggesting they're at reduced risk for heart disease.
But in older women, hormone therapy appears to increase the risk of cardiovascular problems and blood clots, a phenomenon confirmed by a study in this week's British Medical Journal.
And researchers have speculated that a decline in the incidence of breast cancer in recent years is due to a decline in the use of hormone therapy after the WHI results were announced. But a cause-and-effect link is not at all clear.
"I think it's possible that declining use of hormone therapy has contributed at least a little to a decreased incidence rate, but there could be other explanations," Manson said. "There's some suggestion that the decline in breast cancer may have begun as early as 1999, which was well before there was decreasing use of hormone therapy. And there is also some evidence that mammogram screening has decreased over the past several years and that this could contribute to lower rates of detection and diagnosis of breast cancer."
That being said, combined estrogen and progestin has been linked to a risk of breast cancer after four to five years of use. It's not clear if estrogen has a similar risk.
There was some evidence in the WHI study that combination hormone therapy reduced the risk of colon cancer, but the evidence isn't enough to recommend hormones as a preventive strategy, Manson said.
Similarly, while estrogen reduces the risk of fracture and enhances bone density, this benefit would require long-term treatment. Other medications are available and should be tried first, Manson said.
Overall, the bulk of the research today, five years after the WHI, should serve to reassure younger women who may need hormone therapy to alleviate menopausal symptoms.
"The most important reason to go on hormone therapy is for menopausal symptoms," said Dr. Nieca Goldberg, medical director of the Women's Health Program at New York University Medical Center and associate professor of medicine at New York University School of Medicine. "Younger women who need to go on hormone therapy for this reason can relax. But hormone therapy should never be given to women with cardiovascular disease."
Manson added: "I don't think that hormone therapy should be started or continued for the express purpose of preventing cardiac disease or other chronic diseases, because there are known risks. However, this is very different from the situation in a recently menopausal woman who has moderate to severe hot flashes and night sweats which interfere with sleep and quality of life. Hormone therapy is known to be the most effective treatment for menopausal symptoms. It's still a very appropriate short-term treatment, but we still recommend using the lowest effective dose for the shortest duration of time necessary."
Visit the U.S. National Library of Medicine for more on hormone replacement therapy.