That's the conclusion of the latest analysis of the Women's Health Initiative (WHI), a group of major U.S. trials set up to test use of hormone replacement therapy for preventing chronic diseases in healthy, older women.
The WHI was launched in the 1990s, at a time when doctors were prescribing hormone replacement therapy to postmenopausal women to ward off heart disease. The results changed common practice, however.
In 2002, one of the trials was stopped early when researchers found that women taking the hormones -- estrogen-plus-progestin pills -- actually had higher risks of blood clots, heart attack, stroke and breast cancer than placebo users did.
A second trial, looking at estrogen therapy alone, was stopped two years later. Women on the hormone showed no lower risk of heart disease, but did have a slightly elevated rate of blood clots and stroke.
The latest findings, published in the Oct. 2 issue of the Journal of the American Medical Association, do nothing to change the general advice on hormones, according to lead researcher Dr. JoAnn Manson, chief of preventive medicine at Brigham and Women's Hospital in Boston.
"Hormone therapy is not indicated for long-term disease prevention," Manson said.
On the other hand, for women who have recently gone through menopause and are suffering from severe hot flashes, hormone therapy is still the most effective remedy. So short-term use "may be appropriate" for those women, Manson said.
That's not a new recommendation; experts have long said that short-term hormone therapy should be an option for severe hot flashes. But these latest results bolster the belief that hormone therapy is safer for relatively younger women who use it for a finite time, Manson said.
She noted that some doctors seem to have had a "misunderstanding" regarding the original WHI findings, and are reluctant to use hormone therapy even for hot flashes.
"Many women have a hard time finding a doctor who'll prescribe it," Manson said. She added that these latest findings paint "a clearer picture of what the message should be."
The results are based on about 16,600 women who were randomly assigned to take either estrogen/progestin or placebo pills, and more than 10,700 who took either estrogen alone or a placebo. The women were on hormone therapy for about six to seven years before the WHI trials were stopped, and Manson's team followed them for six to eight years beyond that.
Over the longer term, most of the risks originally tied to hormone replacement therapy declined -- and so did the benefits, such as lower risks of hip fractures and diabetes. The exception was breast cancer risk, which remained higher for women who used estrogen and progesterone. Across the study period, there were 434 cases of breast cancer among those women, versus 323 among placebo users.
The findings were "more favorable" among relatively younger women, aged 50 to 59, who used estrogen only, the researchers said. They actually had a slightly lower rate of heart attack and fewer deaths, versus women in their 50s who used placebo pills.
But those differences were small, and Manson said there are concerns about other hormone therapy risks, even in younger women -- such as the risk of blood clots that could cause a stroke or travel to the lungs.
So, no one should take hormones for the sake of cutting ling-term disease risks, said Dr. Elizabeth Nabel, who wrote an editorial published with the study.
"Even though short-term use of this therapy may be helpful in [menopause] symptom relief, this new, 13-year follow-up study clearly does not support the long-term use of hormone therapy for the prevention of chronic diseases," said Nabel, president of Brigham and Women's Hospital.
For a drug to be used to prevent, rather than treat, disease, the benefits have to clearly be worth it, Manson noted. "We have to set the bar very high," she said.
Studies are still looking into whether hormone therapy might cut relatively younger women's disease risks -- including whether lower doses or different "routes of delivery" might work better.
It's thought, Manson said, that hormone patches might be safer than pills, because they may not carry the same blood-clot risk. But there is no conclusive evidence that patches should be used for disease prevention either, she stressed.