Consistently high levels of the stress hormone cortisol are linked to faster memory and thinking decline in older adults, a long-term study published in JAMA Network Open has found.
Researchers tracked changes in the cognitive abilities of 3,895 participants with an average age of about 77 years for up to 11 years. Cortisol levels were measured using saliva samples taken three times a day, in the morning, afternoon, and evening.
The investigation demonstrated that individuals with the highest overall concentration of the stress hormone experienced a faster decline in cognitive functions over time. However, the researchers discovered that the volume of cortisol was not the only determining factor, as the specific pattern of daily concentration changes also played a major role.
Participants who exhibited more pronounced daily fluctuations in cortisol levels showed a slower rate of cognitive decline. In contrast, individuals whose hormone levels remained flatter and more constant across the day suffered a faster decline in memory and thinking capabilities.
Biological role of cortisol in the brain
Cortisol is an essential steroid hormone produced by the adrenal glands, which rest atop the kidneys. As the primary hormone involved in the body's stress response, cortisol regulates a wide array of physiological processes, including metabolism, immune function, blood pressure, and blood sugar regulation.
The hormone acts directly on specific receptors in brain regions responsible for memory and executive function, such as the hippocampus and prefrontal cortex. Because cortisol is released by the body in response to stress and affects areas of the brain involved in memory and thinking, scientists suggested that analyzing daily cortisol level profiles could in the future help identify individuals at an increased risk of cognitive decline.
Despite the clear relationship between cortisol patterns and the pace of memory decline, the researchers found no link between cortisol level characteristics and the risk of developing Alzheimer's disease.
Medical research context and cognitive health
JAMA Network Open is an open-access, peer-reviewed medical journal published by the American Medical Association that covers clinical research across medicine, healthcare, and public health. Age-related cognitive decline encompasses progressive reductions in memory, processing speed, and cognitive flexibility, which can range from subtle age-associated memory loss to severe dementia.
Measuring cortisol via saliva is a standard, non-invasive diagnostic technique frequently utilized in biological research to monitor circadian endocrine rhythms without subjecting subjects to the acute stress of intravenous blood collection.
The new research adds to broader scientific efforts aimed at understanding age-related brain changes and identifying potential therapeutic avenues. Previous studies in cognitive health showed that turmeric extract, specifically the active compound curcumin, may improve memory indicators in people with Alzheimer's disease.
