Saliva Cortisol May Serve as Early Indicator of Cognitive Decline: Study - Video

Abnormal daily patterns and higher overall levels of the stress hormone cortisol may be associated with faster cognitive decline in older adults, according to a study involving nearly 3,900 people.

Researchers analysed data from the Chicago Health and Aging Project, including 2,503 Black and 1,392 White participants with an average age of 76.7 years. Participants were followed for up to 11 years.

Salivary cortisol was measured at three points over a 24-hour period—morning, afternoon and evening—to assess both overall cortisol levels and changes throughout the day.

The researchers found differences in cortisol patterns between Black and White participants. Black participants had lower overall cortisol levels, less variation across the day and a flatter morning-to-evening pattern.

Despite these differences, the relationship between cortisol patterns and cognitive decline was similar in both groups. Participants whose cortisol levels showed greater variation during the day tended to experience slower cognitive decline. In contrast, those with higher overall cortisol levels had faster cognitive decline.

Cortisol is released as part of the body's response to stress and can cross the blood-brain barrier, where it interacts with receptors in brain regions involved in cognition. The findings suggest that long-term changes in stress-related hormonal patterns may be associated with later changes in cognitive function.

However, the researchers did not find evidence that cortisol patterns predicted who would develop Alzheimer’s disease during the follow-up period.

The study also cannot establish that higher cortisol or chronic stress directly causes cognitive decline. Cortisol levels can vary because of multiple factors, and measurements taken at only three time points may not fully capture long-term hormonal patterns.

Longer-term research is needed to determine whether cortisol patterns can help identify people at higher risk of cognitive decline and whether interventions targeting chronic stress could support healthy brain ageing.

REFERENCE: Ng TKS et al. Salivary cortisol and cognitive decline and Alzheimer disease in older adults. JAMA Netw Open. 2026;9(7):e2622955.