By Nicolle Charbonneau
HealthSCOUT Reporter

Worried you won't stay sharp as a tack after menopause? If you have high levels of certain types of estrogen, you may have a little less to worry about, a new study says.

The research suggests that older women with high levels of some estrogens are less likely to suffer cognitive decline after menopause. The findings, which appear in the Aug. 26 issue of The Lancet, support the theory that taking estrogen via hormone-replacement therapy (HRT) after menopause may even help some women ward off Alzheimer's disease.

The researchers say certain estrogens are capable of crossing into the brain, where they can actively ward off the loss of mental skills. Ninety percent of all estrogen molecules are attached to a protein that makes it impossible for the hormone to cross the blood-brain barrier. However, the remainder are either loosely bound or not bound to a protein at all, and can make the leap into your gray matter.

Led by Dr. Kristine Yaffe, an assistant professor of psychiatry, neurology and epidemiology at the University of California, San Francisco, the researchers reviewed measurements of the different types of estrogen, as well as testosterone, in the blood of 425 women age 65 and older. The measurements, done between 1986-88, were matched by Yaffe to the women's scores on a "modified mini mental status examination" (mMMSE), a measure of mental functioning. A decrease of three points or more indicates a loss of mental prowess.

Six years later, the tests were repeated on 295 of the women. Yaffe and her colleagues reviewed that data and found that 17 percent of 106 women originally classified as having "low non-protein-bound estrogen levels" showed signs of mental decline. But only 5 percent of 94 women originally found to have high levels of those estrogens had suffered mental impairment. There seemed to be no link between cognition and testosterone levels.

Yaffe says it's not yet clear how these estrogens may protect mental abilities once they reach the brain. But there are several possibilities. They may protect neurons [brain cells], allow less obstruction of blood flow to brain tissue, and perhaps prevent some amyloid deposition, which is linked to Alzheimer's disease.

The findings raise the possibility of screening women for low levels of estrogens, which could then be raised through hormone-replacement therapy, Yaffe says.

But in an accompanying commentary in the journal, Mary Tierney, associate professor of family and community medicine at the University of Toronto, cautions that more research is needed.

Tierney points out that 27 percent of the 425 women who started the study went on to develop breast cancer -- higher than the average rate among all women. "Twenty-seven percent of the population does not have breast cancer," she says. "It means that you really should replicate the findings in a population that represents postmenopausal women."

Still, Tierney says, the new research "shows that actual levels of hormone in the blood predict how well someone will do cognitively." She suggests that for elderly women, the potential for remaining intellectually sharp might outweigh a small increase in their risk of breast cancer.

Adds Yaffe: "The interesting thing in this study, though, is that the [estrogen] levels overall were not that high, suggesting that maybe low doses of HRT may be enough. These doses then may not raise breast-cancer risk."

What To Do

You can find out about Alzheimer's disease from the National Institute of Neurological Disorders and Stroke, or about breast cancer from the American Cancer Society.

For information about menopause, check out the North American Menopause Society.