The new study, conducted by the Mayo Clinic in the USE, which evaluated three decades of prior research, concluded that hormone therapy to treat symptoms of menopause doesn't increase overall risk of death or the risk of death from heart attack, stroke or cancer.
"This is the latest update of the current evidence," said lead author Dr. Khalid Benkhadra, a research fellow at the Mayo Clinic in Rochester, Minnisota. "I can say there's no risk of dying from any reason because a woman is taking hormone replacement therapy."
The results, Benkhadra said, should allay concerns of some women with debilitating menopausal symptoms who have feared taking hormones.
But not everyone is sold on the safety of hormone therapy. Heart and cancer doctors who reviewed the new findings said that hormone therapy should still be used sparingly on those most in need, until further research proves otherwise.
"This study may provide some comfort that it shouldn't shorten your life, but it doesn't change the concern that the bad effects of hormone therapy are going to be an issue," said Dr. Len Lichtenfeld, deputy chief medical officer for the American Cancer Society.
Lichtenfeld added that the review's results are preliminary, and haven't been subjected to the rigorous peer review necessary for a study to be published in a medical journal.
"No one should change treatment until the data is examined more closely," he said.
Findings from the new review were scheduled to be presented Friday at the annual meeting of The Endocrine Society, in San Diego.
Concerns about the long-term safety of hormone therapy arose more than a decade ago with results from the Women's Health Initiative (WHI), a large-scale federal study of the health problems facing postmenopausal women.
The Women's Health Initiative found that hormone therapy using estrogen and progestin increased a woman's risk of heart attack, stroke, blood clots and breast cancer, compared with placebo. Estrogen alone increased risk of blood clots and stroke, but made no difference in heart attack risk and had an uncertain effect on breast cancer.
"We saw a significant decline in the use of hormone replacement therapy as a result of that study," Lichtenfeld said, with doctors now limiting use of hormone therapy solely to women with severe menopausal symptoms.
The new Mayo Clinic study combines the data from 43 randomized, controlled trials on hormone therapy. The trials included more than 52,000 women. All were 50 or older.
Researchers found that neither of the main hormone therapies -- estrogen alone, or estrogen combined with progesterone - affected a woman's risk of dying from any cause, or specifically from a heart attack, stroke or cancer.
"We just summarized the current evidence, and came down to the conclusion there's no significant effect," Benkhadra said.
The new study confirms one of the lesser-publicized findings from the Women's Health Initiative -- that hormone therapy had no effect on a woman's overall risk of death, said Dr. JoAnn Manson, chief of preventive medicine at Brigham and Women's Hospital, a professor at Harvard Medical School, and one of the WHI's principal investigators.
"Hormone therapy has a complex balance of benefits and risks," said Manson, who also serves as a spokeswoman for the American Heart Association. "The risk of many health outcomes decreased, even while other health outcomes were increased."
For example, hormone therapy reduced women's risk of fractures, colorectal cancer and diabetes in the WHI, even though it increased risk of other potentially fatal conditions, Manson said.
"Because it's such a very complex profile of benefits and risks, all-cause mortality doesn't capture the full picture. For a woman who dies from a stroke, it won't matter to her that there was a neutral effect on all-cause mortality," she said.
"We really recommend personalising the hormone therapy decision-making process to the underlying risk factors of each woman," Manson said, noting that younger women in their 50s and closer to the start of menopause tend to have fewer negative consequences from the therapy. "There's no one-size-fits-all answer."
Until further research is conducted, doctors and patients should stick to the strategy recommended by the U.S. Food and Drug Administration, Lichtenfeld said.
That strategy calls for "the lowest dose of hormone replacement therapy for the shortest period of time," and only for severe menopause symptoms, he said.