In the first long-term study of its kind, researchers at the National Institute on Aging recently used neuroimaging technology to find evidence that the brains of post-menopausal women who receive estrogen replacement therapy (ERT) age differently and have significantly greater blood flow to areas involved in memory formation than the brains of women who do not receive hormone replacement.
These previously unreported physical findings add support to the idea that ERT for post-menopausal women may have an effect on age-related memory problems. The finding also suggests that ERT may lower susceptibility to neurological changes associated with Alzheimer's disease.
The research, conducted by Drs. Pauline Maki and Susan Resnick of the NIA, is reported in the current issue of Neurobiology of Aging.
In their two-year study, Drs. Maki and Resnick used positron emission tomography (PET) scans to produce brain images of 28 cognitively healthy women, all of whom were age 55 or older, as they rested and as they performed memory tasks for words and designs. PET scans, which require highly specialized equipment and are primarily used for research purposes, produce three-dimensional “maps” that provide researchers with information about activity in particular brain regions as a person performs a task or responds to stimuli.
Before the PET scan, the women, 12 who were receiving ERT as part of their regular medical treatment and 16 who were not, were asked to view 20 objects and a list of 20 words on a computer screen. During the scans, the women were shown a series of words or figures—some that they had seen earlier on the computer screen and others that they had not seen before. As they viewed these items, the women were instructed to indicate whether they had seen a word or figure previously. The scan measured the activity of their brains as they tried to remember the studied items. The women underwent a second PET scan under similar conditions 24 months later. Utilizing the PET scans and other computer technology, Drs. Maki and Resnick were able to observe differences in brain blood flow over time between the two groups of women as they performed these cognitive tasks.
Overall, the women using ERT scored higher on memory tests, Dr. Maki said. PET scans showed that over time these women also had increased blood flow in some of the same brain regions that form memory circuits and that are prone to preclinical abnormalities in individuals at increased genetic risk for Alzheimer's disease and in individuals who go on to develop dementia. These brain regions include the hippocampus, parahippocampal gyrus, and middle temporal lobe.
"This study adds credence to prior research that implies estrogen may be beneficial to cognitive aging," Dr. Maki said. "It really gives us the first direct insight into how the brain responds to estrogen over time, and how estrogen might protect against normal and abnormal memory changes as we age."
This paper appears in the de la Torre Special Issue, Neurobiology of Aging, volume 21, Number 2, pages 373-383.