Salivary cortisol patterns predict cognitive decline in older adults

An irregular pattern and consistently higher levels of a stress hormone called cortisol found in the saliva were associated with cognitive decline later in life - Blacks specifically had lower overall cortisol levels and less change in their levels during the day than whites - according to newly published research.

We tested salivary cortisol since it's actively circulating in the body and interacting with organs, including the brain. The study design shows us that there are racial differences in cortisol patterns, which may reflect regular exposure to stress and its lasting impact on communities that face social and economic conditions."

Ted K.S. Ng, PhD, study author and translational gerontologist and neuroscientist at Rush

Over a 24-hour period, cortisol was measured at three points during the day: morning, afternoon and evening.

"The cortisol patterns differed between Black and white participants," Ng said. "Black participants had lower overall levels, less change during the day and a flatter pattern from morning to night. But even with these differences, cortisol patterns were linked to cognitive decline in similar ways in both groups. People with more variation during the day had slower cognitive decline, while those with the highest overall cortisol levels had faster decline."

The study followed 3,895 people with an average age of 76.7. The study included participants from the Chicago Health and Aging Project (CHAP), which included 2,503 Black participants and 1,392 White participants. The CHAP participants in this study were from four neighborhoods on Chicago's South Side and were followed for up to an 11-year period.

"A strength of this study is that more than 60 percent of the study participants were Black older adults," Ng said. "Many studies have been conducted primarily in White populations. This gives us an opportunity to examine differences in cortisol in saliva across racial groups while examining how cortisol patterns affect cognitive decline."

Releasing the hormone cortisol is the body's natural way of responding to stress. Cortisol crosses the blood-brain barrier and binds to receptors in areas of the brain responsible for cognition. This research highlights the potential long-term effects of stress on brain function.

"These findings suggest that this stress-related biomarker may one day identify people who may be at a higher risk for cognitive decline," Ng said. "There are some disadvantages to studies that examine cortisol levels, so there would need to be more studies to examine what's happening over a longer period of time in order to find new ways of supporting healthy cognitive aging."

The study did not find that cortisol patterns predicted who developed Alzheimer disease during the follow-up period.