Newswise, August 25, 2015— MINNEAPOLIS – Testing the
saliva of healthy older people for the level of the stress hormone cortisol may
help identify individuals who should be screened for problems with thinking
skills, according to a study published in the August 19, 2015, online issue of Neurology®,
the medical journal of the American Academy of Neurology.
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.
“Studies have shown that depression increases the
risk for dementia, but we don’t know much about how this relationship occurs,”
said study author Lenore J. Launer, PhD, of the National Institute on Aging in
Bethesda, Md., and a member of the American Academy of Neurology.
“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.”
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.
People with the highest level of cortisol were more
likely to have a smaller overall brain volume than those with lower levels of
cortisol, with a difference of 16 milliliters between the two groups. 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.
To learn more about brain health, please visit www.aan.com/patients.
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. A neurologist
is a doctor with specialized training in diagnosing, treating and managing
disorders of the brain and nervous system such as Alzheimer’s disease, stroke,
migraine, multiple sclerosis, brain injury, Parkinson’s disease and epilepsy.
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