A study from Johns Hopkins and the National Institute on Aging (NIA) adds more evidence that women who use estrogen appear to have less risk of developing Alzheimer's disease (AD).
"We found that women in our study on estrogen replacement therapy (ERT) had a 54 percent reduction in their relative risk of developing Alzheimer's disease," says Claudia Kawas, M.D., an associate Hopkins professor of neurology. "If this connection can be clinically confirmed, we would anticipate a significant public health impact." Only 12 to 15 percent of eligible women in the United States are already on ERT.
Researchers found the link between estrogen and AD by studying long-term health information on 472 women that was gathered for the NIA's Baltimore Longitudinal Study of Aging (BLSA). Results of the study, funded by the NIA, are published in the June issue of Neurology.
Forty-five percent of the women studied had taken estrogen orally or through skin patches. Thirty-four women developed Alzheimer's disease, but only nine were estrogen users.
"We took into consideration the women's education, which is known to affect the risk of AD," explains Kawas. "But we still found drop in risk of Alzheimer's disease for women who reported use of ERT."
Scientists speculate that estrogen may reduce risk of AD by stimulating growth of nerve cells; inhibiting levels of apolipoprotein E, a fatty acid closely linked to heart disease and AD; by deactivating chromosome-damaging oxidants; and by increasing levels of neurotransmitters such as acetylcholine.
Kawas said their study can't rule out the possibility that some other characteristic common to women who use estrogen is causing the reduced risk of Alzheimer's they found. But other recent studies have found a relationship between ERT and reduced risk of AD.
"We need to explore estrogen's potential benefits in a carefully controlled clinical study," says Kawas. "That's particularly important given that some studies suggest that estrogen use produces significant side effects, such as increased risk of breast and uterine cancer."
Other authors on the study were Ann Morrison and Maria Corrada of Hopkins; S. Resnick, A. Zonderman, E. Metter, C. Bacal, and D. Lingle of NIA; and Ronald Brookmeyer of the Hopkins School of Hygiene and Public Health.