By Amy Norton

NEW YORK (Reuters Health) - Older women with naturally higher estrogen levels are less likely to see their mental abilities drop off with age, results of a new study suggest. The findings support the idea that estrogen replacement therapy after menopause may protect women from Alzheimer's disease, researchers report.

In a study of 425 women aged 65 and older, those with relatively higher estrogen levels were less likely than women with lower concentrations to show signs of mental decline over 6 years. Although this boosts the theory that hormone therapy can cut Alzheimer's risk, Dr. Kristine Yaffe told Reuters Health that it is still too early to prescribe estrogen replacement for that purpose.

On the other hand, the findings score ``a big point for team estrogen,'' she said.

Researchers led by Yaffe, of the University of California, San Francisco, report the findings in the August 26th issue of The Lancet.

Studies have yielded conflicting results on whether estrogen wards off mental decline. In her own past research, Yaffe has found evidence that it does not. What makes the current study different, she said, is that her team focused not on each woman's total amount of estrogen, but on the amount of ``free'' or ''loosely-bound'' estrogen in the blood.

Most of the estrogen circulating in a woman's body is bound to protein, which prevents it from passing from the bloodstream into the brain. Free or loosely-bound estrogen, however, can more readily break the blood-brain barrier. From there, it interacts with estrogen receptors in the brain. It is the strategic placement of these estrogen receptors--in brain areas linked to learning and memory--that may explain any protection estrogen provides the brain.

At the beginning of the current study, Yaffe's team measured the women's levels of free estrogen and tested their mental abilities. Six years later, the women took the tests again. When they divided the women into three groups based on their initial free estrogen levels, the investigators found that the group with the highest levels were 70% less likely than those with the least free estrogen to have suffered mental decline.

The association held even when the researchers accounted for factors such as age, education, and whether the women had used estrogen replacement therapy.

An important point in this study, Yaffe said, is that all of the women had relatively low free estrogen concentrations, compared with what younger women would have. This, she noted, suggests that low doses of estrogen may be enough to help prevent dementia--a factor that would be key for women who fear the increased risk of breast cancer that has been linked to estrogen replacement.

One of the ``intriguing'' things about the relationship between Alzheimer's disease and estrogen is that women are actually at higher risk of Alzheimer's than men are, Yaffe pointed out. Researchers believe this is because women experience such a sharp drop in estrogen after menopause, she explained. Men, on the other hand, maintain a fairly steady level of estrogen throughout life. According to Yaffe, this is further evidence that using therapy to counter older women's estrogen drop may cut their Alzheimer's risk.

(From Yahoo)