TORONTO (CP) - Researchers have added a new wrinkle to the debate over the safety of hormone replacement therapy with a
finding that taking estrogen alone may benefit heart health for a certain group of menopausal women.

In a new study, a followup to the massive U.S. Women's Health Initiative (WHI), the researchers found that menopausal women
aged 50 to 59 who took estrogen pills had lower levels of coronary artery calcium compared with women of the same age given a dummy pill.

Coronary artery calcium is an indicator of plaque blockage (hardening of the arteries) that can lead to a future heart attack, said lead author Dr. JoAnn Manson, head of preventive medicine at Brigham and Women's Hospital.

"In a woman who has healthy blood vessels, it (estrogen) seems to slow the early stages of plaque buildup and does not appear to have those risks," Manson said Wednesday from Boston. "It doesn't increase the risk of heart attack."

It is the latest study in recent months to suggest that women who take hormones in early menopause enjoy some health benefits beyond symptom relief. But that's not the case for women who start replacement therapy in their 60s and 70s: the added hormones can actually raise their health risks.

Manson said older women may already have hardening of the arteries, and "estrogen may not only increase the risk of clotting
and blocking off the blood vessel, which is already narrowed, but it may actually increase the risk of plaque rupture," leading to a heart attack.

The danger of heart attack - and other health consequences - linked to hormone replacement therapy has been of increasing concern in the last five years, since initial results from the landmark study scared millions of women away from the once
ubiquitous menopause treatment.

Before the Women's Health Initiative began in the 1990s, studies had suggested that hormones not only relieved hot flashes and other menopause symptoms, but also appeared to protect women against heart disease, osteoporosis and dementia.

But WHI, the largest-ever study of postmenopausal women, published findings in 2002 that contradicted those assertions and
sent up a number of red flags about potentially adverse effects.

One arm of the study, looking at women taking both estrogen and progestin, was abruptly halted in 2002 when evidence showed that taking the hormone combination bumped up the risk of breast cancer, stroke, blood clots and, in the first year of
treatment, heart attack.

The estrogen-alone arm of the study involving women who had undergone hysterectomy was stopped in 2004, a year early, because of concerns that estrogen boosted the risk of stroke and blood clots.

While the initial analysis found that estrogen had no effect on heart attack risk overall among WHI participants, who ranged
in age from 50 to 79, the new study suggests it could benefit women in their 50s and those within 10 years of menopause.

"It's additional reassurance for recently menopausal women that estrogen is not likely to have an adverse effect on their hearts, as the original findings may have suggested," Manson said.

"If they have moderate to severe hot flashes and night sweats that interfere with sleep and disrupt quality of life, hormone therapy remains a viable treatment option."

However, she cautioned that replacement estrogen should be taken for no more than five years, at the lowest effective dose,
and only for relief of moderate to severe hot flashes and night sweats.

"It shouldn't be used for the express purpose of preventing cardiovascular disease. Estrogen is known to have other risks and should be used only for the treatment of menopausal symptoms at the lowest dose for the shortest duration necessary."

The study, published in Thursday's New England Journal of Medicine, showed no heart health benefit for older women or for
those who began taking estrogen more than 10 years after menopause.

The analysis focused on more than 1,000 women in their 50s who had undergone hysterectomy and were taking either estrogen pills or a placebo for an average of 7 1/2 years. The women had cardiac scans in 2005 to check for calcium buildup in their arteries.

The researchers found that those women on estrogen were 30 to 40 per cent less likely to have measurable levels of artery-clogging calcium than those on placebo.

In an accompanying editorial, Drs. Michael Mendelsohn and Richard Karas of Tufts University in Boston said the new findings
support consensus statements from the North American Menopause Society and the International Menopause Society, which endorse the "timing hypothesis" for safe hormone replacement.

However, the senior author of the followup study stressed that hormone therapy still carries other health risks - including an increased danger of blood clots and stroke.

"Heart disease is complex, and the effect of estrogen on one risk factor does not adequately predict the risk of having a heart attack," Marcia Stefanick, a professor of medicine at Stanford University, said in a release.

"But this study offers some reassurance for women of menopausal age that it's not unsafe, in terms of the risk of heart
attack, to take estrogen, at least for a few years."