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High levels of the stress hormone are associated with reduced brain volume and poorer performance on tests of thinking and memory.
American doctors analyzed the results of a large study using data on 4244 people (mean age 76 years) who did not suffer from dementia. By scanning the brain, the volume of the brain of each of them was determined, after which they were tested, where their thinking and memory were tested. Saliva samples were taken from retirees in the morning and evening to determine the level of cortisol (stress hormone). According to the results of the analysis, the study participants were divided into three groups – with high, medium and low levels of cortisol.
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Those older adults who were found to have high levels of cortisol, on average, had a smaller brain volume (especially gray matter) than those who had lower levels of this hormone, a difference of about 16 milliliters. They also scored lower on tests of thinking and memory. However, this association was only valid for evening cortisol measurements. Conversely, high levels of this hormone in the morning have been associated with increased white (but not gray) brain volume and higher scores on some tests (but not memory tests). It is believed that it is the evening analysis that shows the basic level of cortisol at rest, the results of the morning analysis are affected by the recent stress of awakening.
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- Secrets of our brain
Studies show that depression increases the risk of developing dementia, but scientists do not yet know the mechanisms of this process. Cortisol levels are elevated in people with depression, and there is a theory that this hormone has a toxic effect on an area of the brain called the hippocampus, which is important for memory.
“Because we’ve only seen results from one test, we can’t yet say which comes first, whether cortisol levels increase or brain volume decreases. It is possible that the decrease in brain volume during aging reduces its ability to withstand the effects of cortisol, which in turn leads to further loss of brain cells. With a deeper understanding of this relationship, we will try to find ways to reduce the negative impact of cortisol on the brain and thinking, ”says one of the authors of the study, neurologist Lenore Loner (Lenore J. Launer).
Подробнее см. M. Geerlings et al. «Salivary cortisol, brain volumes, and cognition in community-dwelling elderly without dementia», Neurology, August 2015.