Estrogen: Alzheimer's Prevention and Treatment for Women
Alzheimers Prevention
Compared with men, women are at greater risk of developing Alzheimer's disease. But recent studies show that they also have a treatment option unavailable to most men -- the female sex hormone estrogen, which helps prevent, delay, and treat Alzheimer's disease.
Several studies show that women who take estrogen after menopause have an unexpectedly low incidence of Alzheimer's disease. Among women with Alzheimer's, those taking estrogen suffer less severe symptoms and slower mental deterioration. In addition, animal studies show that estrogen improves blood circulation through the brain, and stimulates nerve cell growth in areas of the brain affected by Alzheimer's.
These findings are summarized in a report published in the July 1996 Journal of the American Geriatric Society by Stanley Birge, M.D., a geriatrician at the Washington University School of Medicine in St. Louis. Birge calls these estrogen findings "terribly exciting" and potentially "among the most promising recent discoveries about treating Alzheimer's."
Estrogen boosts the production of acetylcholine, a key chemical (neurotransmitter) involved in the transmission of nerve impulses across the tiny gaps between nerve cells (synapses). Estrogen also impedes the deposition of beta-amyloid, the protein involved in the characteristic plaques of Alzheimer's disease. In addition, estrogen improves blood flow through the brain, and enhances verbal abilities of postmenopausal women who take hormone replacement therapy. Estrogen also helps maintain the integrity of the hippocampus, a structure in the brain involved in memory.
Several lines of evidence show that estrogen helps prevent and treat Alzheimer's disease:
- Several epidemiological studies show that taking estrogen reduces women's risk of Alzheimer's disease. Notably, New York City researchers investigated Alzheimer's risk among 1,124 elderly women. During the follow-up period, the disease developed in 14.9% of them. Among women who had never used estrogen, the figure was 16.3%, while only 5.8% of estrogen users developed Alzheimer's. Among estrogen users, risk decreased with hormone use longer than one year.
- In a 30-week study of 318 women with mild to moderate Alzheimer's disease, all participants took Cognex (tacrine), one of only two drugs currently approved to treat the disease, and some also took estrogen replacement therapy. Compared with those on tacrine only, the women taking tacrine plus estrogen fared better on a number of cognitive measures.
- In an eight-week study of 12 Tacoma, Washington, women with mild to moderate Alzheimer's, all the women received skin patches -- half that released estrogen into the blood, and half that contained a placebo. "The estrogen had a rapid effect," said Sanjay Asthana, M.D., who presented the results at a meeting of the Society for Neuroscience. "Within a week, the women on estrogen showed improvement." By the end of the study, the estrogen users' cognitive test scores had almost doubled. The more estrogen the women absorbed, the greater their mental improvement.
- Finally, as part of the 38-year Baltimore Longitudinal Study of Aging, researchers from the National Institute on Aging assessed 16 year's worth of medical records for 514 postmenopausal women. They found that compared with women who had never taken estrogen, those who had were 54% less likely to develop Alzheimer's disease.
In addition to helping prevent and treat Alzheimer's disease, a great deal of research shows that the sex hormone also helps prevent heart disease, women's leading cause of death, and osteoporosis, bone-thinning that can lead to serious fractures.
"But for all its benefits, estrogen also carries some risks. It may increase breast cancer slightly, although studies remain inconclusive. Estrogen is known to increase uterine cancer risk if a woman takes it without another sex hormone, progesterone.