Women who start hormone therapy toward the beginning of menopause may have a lower risk of developing heart disease, new research suggests.
The study, of over 74,000 Swedish women, found that those who started hormone therapy within five years of beginning menopause typically stayed free of heart disease for a longer time than non-users. In contrast, women who started hormone therapy later showed an increase in their heart disease risk.
"This is in line with what a number of studies have shown," said Dr. Sonia Tolani, of the Women's Center for Cardiovascular Health at New York-Presbyterian Hospital, in New York City.
"There does seem to be a relationship between the timing of hormone therapy and heart disease risk," said Tolani, who was not involved in the study.
However, she stressed, that doesn't mean women should routinely use hormones when menopause begins. For one, studies like the latest one don't prove that early hormone therapy, itself, lowers heart disease risk; they can only show an association between these factors.
And, for over a decade, experts have been advising limited use of hormone therapy, the U.S. National Institute of Aging (NIA) says. Hormone therapy is usually considered an option only for women with more severe menopause symptoms, the NIA noted.
"It should not be used to prevent heart disease," Tolani said.
The findings were to be presented Wednesday at the annual meeting of the North American Menopause Society, in Las Vegas. Study results presented at meetings are generally considered preliminary until they've been published in a peer-reviewed journal.
At one time, menopausal women were routinely prescribed hormone therapy to help ward off heart disease. That all changed in 2002, when researchers reported the findings from the Women's Health Initiative (WHI), a large U.S. clinical trial that tested oral hormone therapy against a placebo.
Contrary to everyone's expectations, the trial found that hormones -- in the form of estrogen plus progesterone -- raised women's risk of blood clots, heart attack, stroke and breast cancer.
As a result, prescriptions for menopausal hormone therapy plummeted.
However, many women in the WHI were well past menopause -- in their early 60s, on average. And a number of studies since have suggested that hormone therapy is safer for younger women, and may even lower their heart disease risks, Tolani explained.
The new findings add to that evidence, she said.
For the study, researchers led by Dr. German Carrasquilla, of the Karolinska Institute in Stockholm, combined the results of five Swedish studies. The studies began between 1991 and 2006. They had information on nearly 75,000 women who were followed for up to 23 years.
During that period, more than 4,700 women developed or died from heart disease. But compared with women who'd never used hormone therapy, those who'd begun it within five years of their first menopause symptoms remained free of heart disease longer -- 1.3 years, on average, the study said.
That advantage was seen even when the researchers accounted for some other major factors, like age, education level, smoking habits, weight and high blood pressure.
However, the study cannot prove hormones deserve the credit, Tolani pointed out. "This isn't going to change practice," she said.
Carrasquilla agreed, and stressed that the study looked only at the risk of heart disease.
He said more research is needed to see how the timing of hormone therapy affects women's risk of stroke, blood clots and breast cancer.
Still, Tolani said, the findings may help reassure women who have severe menopause symptoms who could benefit from hormone therapy.
"There are women who get terrible hot flashes, and that would typically happen early in menopause," she said. "The evidence suggests that if they use hormones for a short time, their risk of coronary heart disease is probably not elevated."
Why would the timing of hormone therapy matter? Carrasquilla said animal research has shown that early hormone therapy helps prevent the buildup of artery-clogging plaques, while delayed therapy does not.
The theory, Tolani said, is that younger women can reap the protective effects of hormone therapy, which include lowering "bad" cholesterol. But hormones can also create inflammation, she noted. And older women are more likely to already have artery-clogging plaques, which could worsen or rupture if there is added inflammation in the blood vessels, she said.