Women who recently learned that hormone therapy can raise their risk of heart disease and other ailments might someday have to consider a potential benefit: that hormones protect against Alzheimer's disease.

Scientists studying elderly women in a Utah county found that those who took the hormones had lower risk of developing the brain disease, which wipes out memory and the ability to carry out simple tasks.

The findings "provide new evidence to suggest a protective effect" of hormone replacement therapy, according to researchers from the Johns Hopkins Bloomberg School of Public Health whose study appears in today's Journal of the American Medical Association.

But Dr. Peter Zandi, lead author of the study, warned that more research is needed before concluding that women should take hormones to prevent the fatal, incurable disorder.

"This is not proof that taking hormone replacement therapy will prevent a woman from developing Alzheimer's disease," he said. Greater clarity could come in the next year from larger studies in which women were randomly assigned either hormones or placebos, experts said.

The Utah study further complicates the debate over whether hormone replacement therapy is helpful or harmful. In July, scientists halted a large study of hormone therapy in post-menopausal women after finding that it raised the risk of heart disease, stroke and breast cancer.

Scientists had expected to find that hormones reduced the risk of cardiovascular disease. Instead, government researchers recommended hormone replacement only for the short-term relief of menopausal symptoms, such as hot flashes and mood swings, but not for prevention of heart disease and other ailments.

After the July announcement, thousands of women went off hormone therapy, though many resumed it when they started experiencing unpleasant symptoms.

In the Alzheimer's study, scientists followed about 3,200 elderly residents of Cache County, Utah, over a three-year period beginning in 1995. They found that women had, on average, about twice the risk of developing Alzheimer's disease as men, but women who had taken hormones for at least 10 years had about the same risk as men.

An 85-year-old man, for instance, had about a 2 percent chance of developing the disease over the course of a year - about the same risk as a woman who had taken hormone replacement for 10 years or more. Women who had never taken the drug ran slightly more than twice the risk that year.

The scientists also found hopeful evidence that women who took hormones for only a few years but started around the onset of menopause reduced their risk of Alzheimer's.

Though it remains to be proved, scientists said it is possible that the hormones can protect nerve cells during a critical time when the brain is experiencing a sudden depletion of the hormone estrogen.

"There might be an important window in the disease process when taking hormone replacement therapy is beneficial in delaying or preventing the onset" of Alzheimer's, Zandi said.

The women in Utah had taken only estrogen.

Today, doctors generally reserve estrogen-only therapy for women who have had hysterectomies because the drug increases the risk of uterine cancer in women whose uteruses have not been removed. A second hormone, progestin, is added for women who have not had hysterectomies because it seems to mitigate the danger of developing uterine cancer.

Dr. Susan Resnick, a researcher with the National Institute on Aging, warned that women should not decide about hormone therapy based on this study, which she called intriguing but preliminary.

"The current information we have is not really sufficient to recommend that women use hormone therapy to protect themselves from Alzheimer's or memory decline," said Resnick, who also wrote an editorial in this week's JAMA.

Further guidance will come from additional data from the Women's Health Initiative, due to be published within the next year, that will show whether estrogen-progestin therapy protected women from getting Alzheimer's, she said.

That study, in which women were assigned either a drug or placebo, is considered a more accurate measure than "observational" studies like the one in Cache County. In the latter, there is the possibility that women who chose to take hormones were healthier because of lifestyle or other factors.

If the drug does prove to prevent Alzheimer's, women will still be left with a difficult choice: Take hormones to prevent mental decline or forgo them because of the risks?

Ultimately, women consulting with their doctors might decide based on family history, Resnick said.