The relationship between basal cortisol levels and cognitive functioning across the adult lifespan

Age-related declines in cognitive functioning have been well documented, however, there are vast individual differences in the age of onset and magnitude of these changes. This observation has spurred the investigation of the potential risk factors for cognitive decline. Chronic elevations of the steroid hormone cortisol have been shown to compromise hippocampal- and frontal cortex- dependent cognitive tasks in rodents, non-human primates and Cushing’s disease patients. Several studies have extended these findings to investigate possible associations between cortisol and cognition in aging human populations. However, these previous examinations of the role of cortisol in cognitive aging have been hampered by the predominant use of single time-point measures of cortisol, small sample sizes, limited age ranges and/or constrained cognitive testing batteries. The present cross-sectional study investigated the relationship between basal cortisol levels, indexed by a 24-hr free cortisol to creatinine ratio, and cognitive functioning on twelve cognitive outcomes in a sample of 1,853 non-demented adults aged 18 to 93 years. The results showed that elevated cortisol levels had small but significant negative effects on verbal learning and working memory performance across the lifespan and significant negative effects limited to older age on a measure of speeded processing. Longitudinal investigation is warranted to examine if within-person changes in cortisol level predict cognitive change.M.S