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Alzheimer’s Disease Could be Detected by Testing Saliva for Cortisol Levels

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 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.

This is a drawing of a brain slice from an Alzheimer's patient.

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. Image is for illustrative purposes only.

“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.

About this Alzheimer’s disease research

Funding: The study was supported by the National Institutes of Health, National Institute on Aging, Icelandic Heart Association and Icelandic Parliament.

Source: Rachel Seroka – AAN
Image Credit: The image is in the public domain
Original Research: Abstract for “Salivary cortisol, brain volumes, and cognition in community-dwelling elderly without dementia” by Mirjam I. Geerlings, Sigurdur Sigurdsson, Gudny Eiriksdottir, Melissa E. Garcia, Tamara B. Harris, Vilmundur Gudnason, and Lenore J. Launer in Neurology. Published online August 19 2015 doi:10.1212/WNL.0000000000001931


Abstract

Salivary cortisol, brain volumes, and cognition in community-dwelling elderly without dementia

Objective: We investigated the associations of morning and evening salivary cortisol levels with regional brain volumes and cognitive functioning in community-dwelling older persons without dementia.

Method: From the Age, Gene/Environment Susceptibility (AGES)–Reykjavik Study, we included 4,244 persons without dementia (age 76 ± 5 years, 58% women) who had 1.5T brain MRI, assessment of cognitive functioning, and saliva collected at home 45 minutes after awakening and at night. Linear regression analysis was used to estimate the cross-sectional relationship among cortisol levels, brain volumes, and cognitive functioning, adjusting for covariates.

Results: Higher evening cortisol was associated with smaller total brain volume (highest vs lowest tertile −16.0 mL; 95% confidence interval −19.7 to −12.2 mL, adjusted for age, sex, education, intracranial volume, smoking, steroid use, white matter lesions, and brain infarcts on MRI). The smaller volumes were observed in all brain regions, but were significantly smaller in gray matter than in white matter regions. Poorer cognitive functioning across all domains was also associated with higher evening cortisol. Higher levels of morning cortisol were associated with slightly greater normal white matter volume and better processing speed and executive functioning, but not with gray matter volume or with memory performance.

Conclusions: In older persons, evening and morning cortisol levels may be differentially associated with tissue volume in gray and white matter structures and cognitive function. Understanding these differential associations may aid in developing strategies to reduce the effects of hypothalamic-pituitary-adrenal axis dysfunction on late-life cognitive impairment.

“Salivary cortisol, brain volumes, and cognition in community-dwelling elderly without dementia” by Mirjam I. Geerlings, Sigurdur Sigurdsson, Gudny Eiriksdottir, Melissa E. Garcia, Tamara B. Harris, Vilmundur Gudnason, and Lenore J. Launer in Neurology. Published online August 19 2015 doi:10.1212/WNL.0000000000001931

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