Women who take hormones for years run a higher risk of Alzheimer's or other types of dementia, according to yet another startling study that turns upside down what doctors have long believed about supplements.

"It's another nail in the coffin" for the use of hormones during and after menopause, said St. Louis gynecologist Dr. Robert Blaskiewicz, a Saint Louis University professor.

The study appears in Wednesday's Journal of the American Medical Association.

The findings in women 65 and older challenge the long-held notion that estrogen-progestin supplements can help women keep their minds sharp -- a belief that was based on smaller, less rigorous studies.

Last summer, a government study was abruptly halted after finding an increased risk of breast cancer, heart attacks and strokes in women who took one type of combined hormone pill.

That finding shattered the conventional thinking about the health benefits of hormones and prompted millions of American women to stop taking supplements.

Some experts say that based on what is now known about supplements, women past menopause should not take hormones at all. Other experts say that women needing relief from night sweats and other menopausal symptoms should take the lowest possible dose for the shortest time.

The new findings on dementia come from a subset of participants in last summer's study. Despite those earlier findings, many women have continued using supplements to relieve menopausal symptoms and in hopes of preventing memory loss and other mental decline, said Sally Shumaker, a public health professor at Wake Forest University who led the latest research.

Women in the study who took hormones for an average of more than four years faced double the risk of developing Alzheimer's or other forms of dementia, compared with those on dummy pills. That means that in one year, for every 10,000 women taking hormones, there will be 23 more cases of dementia.

Researchers also found that hormones did not protect against less severe mental decline, such as mild memory loss.

One possible explanation for the confounding new findings is that hormones raise the risk of strokes -- and strokes are known to cause brain damage and contribute to dementia, the researchers said.

Will women change their minds?

Nevertheless, the increased risk of dementia is very small, said Marilyn Albert, head of the Alzheimer's Association's scientific advisory council and a Johns Hopkins University neurology professor.

Age remains the single greatest risk factor for dementia, and the study suggests that a 65-year woman on estrogen-progestin pills "would have the increased risk profile of a 70-year-old woman not taking hormone replacement therapy," Albert said.

Dr. Judith Salerno, deputy director of the National Institute on Aging, said the results indicate older postmenopausal women should not use estrogen-progestin supplements in hopes of keeping their minds sharp.

"There is no benefit, and possible harm, for older women taking this therapy," she said.

Cindy Yeast, a 50-year-old Washington-area publicist, called the findings disappointing. She started taking supplements two years ago -- partly to stave off mild dementia that affects her elderly parents. Still, she said she is not sure the new findings will change her mind.

"Every time a new study comes out, you can't just react," Yeast said. "You have to weigh what is this doing for me now."

The results come from the Women's Health Initiative Memory Study, which involved 4,532 women who used Prempro estrogen-progestin pills for an average of more than four years. It was funded in part by Prempro maker Wyeth Pharmaceuticals.

Probable dementia was diagnosed in 61 women -- 40 in the hormone group and 21 taking placebo pills.

The notion that hormone supplements are good for the mind has been around for at least a decade. Doctors have speculated that estrogen protects against cell damage and improves blood flow.

Wyeth estimates that 1.2 million women are still taking Prempro pills, down from about 3.4 million before the study was halted last summer. Other types of hormone supplements include patches and creams.

Wyeth's Dr. Victoria Kusiak said it is unclear whether the disappointing results would apply to younger patients. Still, she said she agrees with those doctors who say that hormones should be used only to treat menopause symptoms such as night sweats and hot flashes "for the shortest duration and the lowest dose."

An arm of the Women's Health Initiative study involving estrogen-only supplements in women who have had a hysterectomy is continuing. Estrogen alone is not recommended for women with intact wombs because it increases the risk of uterine cancer.