This study was published in the August 19, 2015, online issue of Neurology®, the medical journal of the American Academy of Neurology.
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- The study found that people with higher levels of cortisol in the evening were more likely to have a smaller total brain volume and to perform worse on tests of thinking and memory skills.
- “High levels of the stress hormone cortisol have been found in people with depression, and the theory is that cortisol has a toxic effect on the hippocampus area of the brain, which plays an important role in memory.” ~ Lenore J. Launer, PhD, of the National Institute on Aging, and a member of the American Academy of Neurology.
- The study involved 4,244 people with an average age of 76 who did not have dementia. Participants had a brain scan to look at brain volume and took tests of their thinking and memory skills.
- Saliva samples were taken from the participants once in the morning and in the evening to determine cortisol levels. Participants were divided into three groups based on cortisol levels of high, medium and low.
Those with the highest level of cortisol also performed worse on the memory and thinking tests than those with low levels of the hormone.
“Since this study just looked at a snapshot in time, we don’t know which came first: the high levels of cortisol or the loss of brain volume,” Launer said. “It’s possible that the loss of brain volume that can occur with aging leads to a lesser ability of the brain to stop the effects of cortisol, which in turn leads to further loss of brain cells. Understanding these relationships may help us develop strategies to reduce the effects of cortisol on the brain and thinking skills.”Launer noted that a limitation of the study was that cortisol was tested only during one day, but said that the large size of the study may balance out that limitation.
The study was supported by the National Institutes of Health, National Institute on Aging, Icelandic Heart Association and Icelandic Parliament.
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The American Academy of Neurology, an association of more than 28,000 neurologists and neuroscience professionals, is dedicated to promoting the highest quality patient-centered neurologic care.
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