Estrogen has been touted as the hormone that keeps women's brains young and lively, and estrogen therapy has been thought to maintain lucidity in postmenopausal women. A group of researchers from all over the United States challenged this assumption in two separate studies recently published.

What the researchers wanted to know: Does hormone therapy benefit the cognitive functioning in postmenopausal women?

What they did: The researchers used data from a long-term study of postmenopausal women called the Women's Health Initiative. For a part of that study looking at hormone therapy, participants, about 27,000 women, were assigned to either estrogen pills (if they had a hysterectomy), estrogen plus progesterone (another hormone) pills, or a placebo. Out of that group, 7,500 women, all between the ages of 65 and 79 at the beginning of the study, agreed to participate in memory studies and , and took tests designed to assess their vocabulary, memory, writing, and a variety of other cognitive skills.

What they found: Neither estrogen therapy nor estrogen plus progesterone therapy improved cognitive functioning. If anything, both regimens of hormone therapy seemed to increase the risk of dementia and lower cognitive functioning, though neither of the two therapies was very different from the placebo. The risk was higher for women who were at a lower level of cognitive functioning in the initial test, though women who scored high did not get any benefits from hormone therapy either.

What it means to you: The hormone therapy trials in the Women's Health Initiative were stopped early because of increased health risks such as stroke and heart attack for women taking active pills. Now, add to the list of the negative effects of therapy a possible decline in cognition or increased risk of dementia. These results did not positively conclude that estrogen and progesterone harm the brain, but those hormones sure don't seem to help it.

Caveats: These women all began hormone therapy well after menopause, at age 65 or older. Studies on animals have shown that, when hormones are given closer to the time of menopause, the positive effect is much more pronounced. There's a possibility that, if given to younger women, estrogen therapy might be beneficial though, in the current study, women who had taken hormones prior to enrolling in the trial did not score higher than those who had not.

Find out more: Information about the Women's Health Initiative, including the results of the hormone studies is available at: http://www.nhlbi.nih.gov/whi/

Read the article: Shumaker, S.A. et al "Conjugated Equine Estrogens and Incidence of Probable Dementia and Mild Cognitive Impairment in Postmenopausal Women." Journal of the American Medical Association. June 23, 2004, Vol. 291, No. 24, pp.2947–2958.

Abstract online: http://jama.ama-assn.org/cgi/content/abstract/291/24/2947

Espeland, M.A. "Conjugated Equine Estrogens and Global Cognitive Function in Postmenopausal Women." Journal of the American Medical Association. June 23, 2004, Vol. 291, No. 24, pp. 2959–2968.

Abstract online: http://jama.ama-assn.org/cgi/content/abstract/291/24/2959