Salivary Cortisol Rhythms Linked to Cognitive Decline in Older Adults
Recent research published by investigators at Rush University Medical Center suggests that daily patterns and levels of salivary cortisol—a primary stress hormone—can serve as an indicator of cognitive decline later in life. While the study identified notable variations in cortisol rhythms between Black and white participants, the ultimate association between the stress biomarker and brain function remained consistent across both demographics.
Understanding the Role of Cortisol in Brain Health
Cortisol is naturally produced by the body as a physiological response to stress. When released, it is capable of crossing the blood-brain barrier and binding to specific receptors located in regions of the brain that govern cognitive processes. To explore the long-term implications of this process, scientists evaluated actively circulating cortisol found in saliva, which interacts directly with bodily organs, including the brain.
Dr. Ted K.S. Ng, a translational gerontologist, neuroscientist, and study author at Rush University Medical Center, explained the rationale behind the methodology. By testing salivary cortisol, the research team sought to understand how chronic exposure to stress influences neurological health over time. The findings underscore the potential long-term neurological impacts of environmental and psychological stress.
Key Findings on Daily Stress Rhythms and Cognition
The investigation tracked 3,895 participants with an average age of nearly 77 years. Over a 24-hour period, researchers measured cortisol levels at three distinct intervals: morning, afternoon, and evening. Participants were drawn from the Chicago Health and Aging Project (CHAP), encompassing individuals from four neighborhoods on Chicago’s South Side who were followed for up to 11 years.
The study cohort included 2,503 Black participants and 1,392 white participants, giving researchers a robust foundation to compare racial differences. According to Dr. Ng, one of the notable strengths of the work was the high representation of Black older adults, a demographic often underrepresented in previous neurological research.
The analysis revealed distinct differences in cortisol profiles between the two groups:
- Black participants exhibited lower overall cortisol levels throughout the day.
- Black participants showed less diurnal change and a flatter overall pattern from morning to night compared to white participants.
- Despite these physiological differences, the relationship between cortisol patterns and cognitive decline followed a similar trajectory in both groups.
Regardless of race, individuals who demonstrated greater daily variation in cortisol levels experienced a slower rate of cognitive decline. Conversely, participants with the highest overall cortisol levels and flatter daily rhythms suffered from faster cognitive deterioration. However, researchers noted that the cortisol patterns observed in this study did not predict the development of Alzheimer’s disease during the follow-up period.
Implications for Future Health and Aging
The researchers suggest that disparities in cortisol profiles may reflect regular exposure to chronic stress, as well as the lasting neurological impacts of adverse social and economic conditions within specific communities. Dr. Ng emphasized that utilizing stress-related biomarkers could eventually help clinicians identify individuals at elevated risk for cognitive decline.
Despite these promising insights, experts caution that further investigation is necessary. Because measuring cortisol presents certain methodological challenges, longitudinal studies spanning longer durations must be conducted to fully understand how to support healthy cognitive aging and develop targeted interventions.
Source: News-Medical.net
