A new report suggests that for women who have had hysterectomies, taking estrogen does not increase the risk of heart disease and may even protect the heart in those who are younger, from 50 to 59.
The findings, being published today in The Archives of Internal Medicine, concern the use of estrogen alone and differ from earlier studies of estrogen and progesterone. The studies of combined hormones found that they increased the risk of heart disease, breast cancer and other ailments.
The new results lend support to a theory held by some researchers, that hormone therapy may help prevent heart disease if women start it early in menopause, but may have no benefit or even cause harm if women start it later. The theory has not been proved.
The new results do not warrant any changes in the current guidelines for hormone use, said Dr. JoAnn E. Manson, an author of the study and a professor of medicine at Harvard. The guidelines say hormones should be used only to relieve symptoms like hot flashes and night sweats, not to prevent heart disease, and should be taken in the lowest doses and for the shortest time possible.
The new report does not apply to most menopausal women, just to those who have had hysterectomies, the only women in the study. The difference is important because the two groups take different forms of hormone therapy. Women who have had hysterectomies can take estrogen alone. But other women cannot, because it can cause uterine cancer. For them, estrogen must be combined with another hormone, a form of progesterone, to counter the cancer-causing effect.
The study being reported today included 10,739 women 50 to 79 who had hysterectomies. It was part of the Women's Health Initiative, a large federally financed study.
The part of the study in which women took combined hormones was halted ahead of schedule, in 2002, because women taking hormones had a slightly increased risk of breast cancer.
In the estrogen-only arm of the study, women were picked at random to receive either estrogen or a placebo. Those on estrogen took 0.625 milligrams a day of Premarin, the most widely used brand of ''equine estrogens,'' named for its source, the urine of pregnant mares.
The original plan was for the women to keep taking estrogen while researchers tracked their health for eight and a half years. The study was stopped early, after 6.8 years, because there was an increased risk of stroke in the women taking estrogen. Estrogen can also increase the risk of blood clots, and in older women it may increase the risk of dementia.
The new report looks at heart disease. Over all, there was no significant difference between the two groups: 201 women on estrogen had heart attacks or died from heart disease, compared with 217 women taking placebos.
But when the researchers analyzed the results by age, they found several areas in which the youngest women, those 50 to 59, did appear to benefit. Those taking estrogen were less likely to need bypass surgery or other procedures to restore blood flow to the heart.
When the researchers looked at a combination of heart problems, including heart attack, death from coronary disease, being hospitalized for chest pain or needing bypass surgery or other procedures, the younger women on estrogen also had a lower risk. The differences were statistically significant, Dr. Manson said.
The findings mean that more research is needed to determine whether the risks and benefits of hormone treatment differ depending on age and other risk factors, Dr. Manson said, adding that it was an oversimplification to say that ''hormones are good for all women or bad for all women.''
But the National Women's Health Network criticized the findings, suggesting that the researchers were interpreting the data to favor hormone use.
Several studies are under way to study hormone doses and routes of administration -- patch versus pill -- in younger women. In the meantime, Dr. Manson and other researchers said, younger women who want to take estrogen to relieve their symptoms may take some reassurance from the latest findings.
