Older women who use certain forms of hormone replacement therapy seem to perform better on tests of memory and mental speed than other women do, a new study finds.

In a four-year study of 3,130 French women age 65 and older, researchers found that those currently on hormone replacement therapy (HRT) performed better on certain cognitive tests. Those who had used HRT in the past but were no longer on it showed no such advantage.

The findings, published in the journal Neurology, conflict with a widely publicized 2003 U.S. study that linked HRT to an increased dementia risk among older women.

However, women in that study were given a particular oral formulation of HRT called Prempro, which combines estrogen and synthetic form of progesterone called medroxyprogesterone.

In contrast, women in the current study were mostly using HRT skin patches with a different combination of estrogen and a natural progesterone, explained lead researcher Dr. Joanne Ryan of the French national research institute INSERM.

That, she told Reuters Health in an email, may help explain the benefits.

Still, no one is recommending that women use any form of HRT for the sake of warding off dementia.

HRT is effective for menopausal symptoms like severe hot flashes and vaginal dryness, but it also carries risks. In 2002, a large U.S. clinical trial called the Women’s Health Initiative (WHI) found that women given Prempro had higher risks of heart attack, stroke, breast cancer and blood clots than women given a placebo.

So experts recommend that women who do try HRT for menopausal symptoms use the lowest dose for the shortest time possible.

“Women should still be cautious when using” HRT, Ryan said. She added that any woman considering hormone replacement needs an individual assessment to see whether the potential benefits outweigh the risks for her.

For their study, Ryan and her colleagues followed 3,130 women age 65 and older, 15 percent of whom were currently on HRT at the start of the study.

Overall, the study found, HRT users tended to score better on certain measures of memory and mental speed at the outset; they also showed a lesser decline in so-called psychomotor speed - the amount of time it takes a person to process and react to a signal.

There was no evidence that hormone therapy reduced women’s risk of developing dementia over the four-year study. However, among women with a gene variant linked to increased Alzheimer’s risk - called ApoE4 - HRT users had no increased risk of dementia during the study period.

The finding, according to Ryan, raises the possibility that HRT might benefit women who are genetically predisposed to developing dementia. She said that future studies should continue to examine that question.

SOURCE: Neurology, November 24, 2009.