A study of 3,895 older adults found that specific patterns of the stress hormone cortisol in saliva are associated with the speed of cognitive decline over time.

Research published in JAMA Network Open indicates that irregular patterns and higher levels of salivary cortisol are linked to cognitive decline in older adults. The study, which followed 3,895 participants for up to 11 years, observed distinct differences in cortisol levels between Black and white participants, though the association with cognitive decline remained consistent across both groups.

Study methodology and findings

Researchers measured cortisol levels at three points—morning, afternoon, and evening—over a 24-hour period. Participants had an average age of 76.7 and were drawn from the Chicago Health and Aging Project, including 2,503 Black participants and 1,392 white participants from Chicago's South Side. The study found that individuals with more variation in their cortisol levels throughout the day experienced slower cognitive decline, while those with the highest overall levels faced faster decline.

Racial differences in cortisol patterns

The study noted that Black participants exhibited lower overall cortisol levels and a flatter pattern of change from morning to night compared to white participants. Study author Ted K.S. Ng suggested these differences might reflect regular exposure to stress and the lasting impact of social and economic conditions on specific communities. While the research identified these variations, it did not find that cortisol patterns predicted the development of Alzheimer's disease during the follow-up period.