エストロゲンは閉経後婦人の記憶力を改善させるらしい
1999年4月11日
米国エール大学の研究によると、エストロゲン補充療法を行っている閉経後婦人は記憶力も改善するという。これは記憶力そのものを改善するよりも脳の活動を若い人のように活発にするためらしい。
Estrogen may improve memory in post-menopausal women
CHICAGO (AP) -- Post-menopausal women undergoing estrogen treatment may also be improving their memories, researchers reported Wednesday in the Journal of the American Medical Association.
The study at the Yale University School of Medicine of 46 post-menopausal women found that estrogen increased activity in regions of the brain associated with memory.
Although the study did not find memories had improved, researchers said estrogen may stimulate the brain to make the type of neural connections typically seen in younger people. They believe that the increased brain activity should mean an accompanying improvement in memory.
"It suggests that the neural circuitry in memory for mature individuals ... can be changed" by estrogen, said Dr. Sally Shaywitz, one of the study's authors. "It is a very hopeful sign."
Production of estrogen, a female hormone, drops sharply after women reach menopause. Previous research has found that estrogen protects against heart disease, fights brittle bones, decreases the risk of colon cancer and may help women live longer.
Studies have also suggested that estrogen may reduce the risk of Alzheimer's disease. The ability to establish new connections in the brain is what is lost with the onset of Alzheimer's.
An expert not involved in the study said the research was significant as another demonstration that estrogens have positive effects on certain aspects of mental function.
"What this study suggests is that what estrogen can do is rewire the central nervous system," said Dr. Stanley Birge, a professor of geriatrics and gerontology at the Washington University School of Medicine in St. Louis. "Perhaps even in the 70- or 80-year-old individual we have the potential" for such regeneration.
Estrogen replacement therapy, however, also carries risks. Studies show it can increase the risk of breast cancer and endometrial cancer.
Shaywitz said estrogen "is not some magic pill," and further study is needed on its benefits and potential side effects.
The researchers used functional magnetic resonance imaging to measure brain activity as the women conducted tasks involving verbal and visual memory. The women -- who ranged in age from 33 to 61 -- were treated with either estrogen or a placebo in a random trial from 1996 through 1998.
Researchers cautioned that while they observed increased brain activity in women given estrogen, there was no subsequent improvement in verbal and nonverbal memory tasks.
Shaywitz said the lack of quantifiable evidence pointing to improved memory function was probably because the tasks were simple and almost all were performed correctly. If a participant was asked something she did not know, the MRI would measure her effort rather than her memory function, she said.
"This is one step ... but this a good step in that it does show a physiological change in areas of the brain related to memory," said Dr. Rodrigo Kuljis, a neurologist at the University of Miami School of Medicine who was not involved in the study.