The researchers, led by Dr. Domonick Wegesin, assistant professor of neuropsychology (in neurology and in the Gertrude H. Sergievsky Center), say their findings have both clinical and research implications. Improvements in measures of consistency, they say, can be added to the list of the benefits of estrogen therapy, which already include decreased risk of Alzheimer's disease, osteoporosis and stroke.
The results also may help neuroscientists localize areas in the brain where estrogen and aging may impact function. Since the ability to perform consistently has been associated with intact frontal lobe function, the findings suggest estrogen may mediate changes in cognitive abilities via the frontal lobe. Also, one's ability to perform consistently decreases with age. Therefore, changes in consistency with age may be related to age-related changes in frontal lobe function.
Consistency differs from overall memory ability and is a relatively new area in research about the neuropsychology of aging. Traditionally, memory is assessed on one occasion, or on a few occasions over a period of time, such as a year. Consistency measures memory capability on multiple administrations of the same test or on several related tests in a short period of time.
An individual may perform very well on both memory and consistency scores. (He or she would have a high average score and a high consistency score.) Another may obtain a low score on the memory tests repeatedly, achieving a poor average score but a high consistency score. Yet another person can score high on some administrations of a test and low on others, getting an average high score, but a low consistency score.
In the study, 48 postmenopausal women between the ages of 60 and 80 and 16 younger women between the ages of 18 and 30 were asked to remember certain words from two lists of four sentences. They repeated each test 16 times with different sentences. The researchers split the older women into three groups: 16 non-hormone users, 16 estrogen-users and 16 estrogen and progesterone-users. None of the younger women used hormones, including any type of birth control. Participants were asked to respond as quickly as possible. Measures of consistency included how accurately they remembered the words on the memory test, as well as how quickly they responded to the memory test items.
Younger women and older women taking estrogen performed more consistently than the older women not taking the hormone, the researchers found. The younger women and the older women taking the hormone also had higher overall memory scores than the women not taking estrogen.
The researchers also found women taking a combination of estrogen and progesterone did not perform as consistently as the estrogen-only users. This finding suggests progesterone may block some of the beneficial effects of taking estrogen alone. The results of the study suggest estrogen use by itself may temper the negative impact of aging on certain brain functions, particularly those related to the frontal regions of the brain.
While the participants completed the memory tasks, the researchers made recordings of the electrical activity of the brain, an electroencephalograph (EEG). The next step in the study is to examine the variability in the electrical activity of the brain across the 16 test runs. The researchers predict brain activity in the older adults will be more variable than the brain activity of the younger adults and that the brain activity of the older women not taking hormones will be more variable than the brain activity of the estrogen-users. They expect the frontal lobe to show this variability.
The study results are being presented by Dr. Wegesin on Sunday, Nov. 11 at the Society for Neuroscience meeting being held in San Diego from Nov. 10 to 15.
·The National Institute of Aging supported the study.
·Other participants in the research were Dr. David Friedman, professor of clinical psychology (in psychiatry); Nina Varughese, a research assistant in the Sergievsky Center; and Dr. Yaakov Stern, professor of clinical neuropsychology in neurology and psychiatry in the Sergievsky Center and the Taub Institute for Research on Alzheimer's Disease and the Aging Brain.