JAMA: High Salivary Cortisol Levels Are Associated With Memory Decline

People with higher overall cortisol levels experience faster cognitive decline over the following 11 years, while those whose hormone levels fluctuate more significantly throughout the day experience slower decline. This is the conclusion reached by researchers from Rush University after analyzing data from nearly 3,900 older adults. The findings were published in JAMA Network Open.

Cortisol is produced in response to stress, and its concentration normally changes throughout the day: levels are higher in the morning and lower in the evening. In the study, researchers measured cortisol levels in saliva in the morning, afternoon, and evening, and then compared these measurements with changes in participants’ cognitive function.

The study included 3,895 people with a mean age of 76. They were followed for 11 years as part of the Chicago Health and Aging Project.

The researchers found that participants with the highest overall cortisol levels experienced faster cognitive decline. At the same time, greater variability in hormone levels throughout the day was associated with slower memory decline.

Cortisol levels also differed between groups. Black participants had lower overall hormone concentrations and less pronounced changes over the course of the day than White participants. However, the association between cortisol measures and changes in cognitive function was observed in both groups.

The researchers note that cortisol may affect the brain because it can cross the blood-brain barrier and bind to receptors in areas involved in cognitive processes. Differences in cortisol levels and its daily fluctuations may reflect prolonged exposure to stress.

However, the study did not show that cortisol can predict the development of Alzheimer’s disease. The authors say further research is needed to understand how long-term changes in the hormone are associated with brain aging.

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