Background: The hormone 'cortisol' has been associated with cognitive deficits in older ages, and also with childhood cognition. The extent to which the associations of cortisol with cognitive deficits in later life reflect associations with childhood cognition ability is unclear. This study aimed to assess associations between adult cortisol levels and subsequent cognitive functions, while considering childhood cognition and other lifetime covariates.
Method: Data are from the 1958 British Birth Cohort. Two morning salivary cortisol samples were obtained at 45 years: 45 min after waking (t1) and 3 h later (t2). Standardized tests assessing immediate and delayed verbal memory, verbal fluency and speed of processing were administered at 50 years. Information on cortisol, cognitive outcomes and covariates [e.g., birthweight, lifetime socio-economic position (SEP), education, smoking and drinking habits, body mass index (BMI), menopausal status, and depression/anxiety] was obtained for 4655 participants.
Results: Worse immediate and delayed verbal memory and verbal fluency at 50 years were predicted by elevated t2 cortisol at 45 years. For instance, for 1 standard deviation (s.d.) increase in t2 cortisol, individuals scored -0.05 s.d. lower on verbal memory and fluency tests. Childhood cognition explained about 30% of these associations, but associations with adult cognition remained.
Conclusions: This study suggests that higher cortisol levels in late morning at 45 years are associated with poorer verbal memory and fluency at 50 years, with a contribution from childhood cognition to these associations.