Women who took estrogen suffered less hardening of the arteries than those who took dummy pills, researchers reported in Thursday's New England Journal of Medicine.
It was the latest study in recent months to suggest that women who take hormones at the start of menopause seem to gain some health benefits beyond relief from hot flashes. That is in sharp contrast to women who raise their health risks when they take hormones in their 60s and 70s.
In general, experts' advice hasn't changed: Use hormones only as needed to treat hot flashes, sleeplessness and other symptoms at the start of menopause. And use the lowest possible dose for the shortest possible time — no longer than four or five years.
"No one is saying that hormones should be used to prevent heart disease," says CBS News Early Show health correspondent Dr. Emily Senay.
"The new thinking is about a woman's age and about the timing, when you use the hormone replacement therapy," Senay told co-anchor Hannah Storm. "Not everyone agrees with this and this data is highly specific to the group of women just studied in this particular study."
The new study is the latest attempt to sort out how menopause hormones affect the risk of cancer, Alzheimer's disease, stroke and heart problems, and whether those risks and benefits differ by age.
The research concludes that women who started taking estrogen pills in their 50s were 30 to 40 percent less likely to have measurable levels of blockage-causing calcium in the arteries that lead to the heart.
"It seems to be slowing the rate of plaque buildup," said Dr. JoAnn Manson, chief of preventive medicine at Brigham and Women's Hospital, the study's lead author.
The research is based on the Women's Health Initiative, a huge federal study started in the 1990s that focused on the risks and benefits of menopause hormones for women.
One phase of the study was suspended in 2002 after researchers detected higher rates of heart attacks, strokes, breast cancer and other problems in women who took an estrogen-progestin combination pill. Many women were startled by the findings; millions stopped taking hormones.
"The heart attack issue was really the thing that surprised us all," said Dr. Michelle Warren, a Columbia University expert who is a consultant for Wyeth Pharmaceuticals, which makes which makes top-selling hormone pills Prempro and Premarin.
Another phase of the big women's study was stopped in 2004 when researchers saw higher risks for strokes and blood clots in women who took estrogen alone. (Levels of heart disease and breast cancer were unaffected by the solo pill.)
Since then, some scientists have begun to slice the large study's data for more nuanced meaning. They note that most of the women in the study were in their 60s or 70s, several years post-menopausal when the research began. New analyses are focusing on women who were in their 50s when they joined the study.
The scientists are researching a "timing hypothesis" that proposes that estrogen can help against clogged arteries and heart disease, but only when given before problems develop and before natural estrogen levels have been low for an extended period of time. Estrogen can trigger heart attacks in women who have advanced atherosclerosis, experts said.