Stress Hormone in Saliva Could Predict Mental Decline
Scientists may be able to identify people at risk for mental decline by measuring the level of the stress hormone cortisol in their saliva.
Researchers at the National Institute on Aging wanted to better understand the theory that cortisol acts as a toxin on the hippocampus area of the brain, leading to depression and affecting memory. So they analyzed cortisol levels, brain volume and cognitive skills of 4,244 healthy adults with an average age of 76.
Cortisol levels of participants were recorded from two saliva samples taken 45 minutes after awakening in the morning and again in the evening. The cortisol levels determined which of three groups a participant was allocated to - high, medium, or low.
Next, the participants’ brains were scanned with magnetic resonance imaging (MRI), providing information on brain volume. Lastly, participants took part in memory and thinking skills tests.
The results showed that compared with subjects in the low cortisol group, those with high cortisol levels had overall brain volumes around 16 millimeters smaller. The volume differences were most noticeable in gray matter regions of the brain as opposed to white matter regions. Additionally, participants with high cortisol levels showed poorer memory and thinking performance on the cognition tests compared to those with low levels of cortisol.
Because the findings examined the effects of cortisol only in a short period of time, researchers were unable to determine which happens first - loss of brain volume, or increased levels of cortisol.
The findings, published in the journal Neurology, could lead to saliva tests that would determine an individual’s risk of Alzheimer’s disease or other forms of dementia, as well as stress reduction strategies for reducing damaging effects of cortisol on cognitive function.