Hair cortisol and dehydroepiandrosterone and their associations with optimism and pessimism in older people.

The cumulative negative effects of prolonged Hypothalamic-Pituitary-Adrenal axis (HPA axis) activation are associated with several age-related diseases. Some psychological traits such as optimism and pessimism have been shown to be related to both health and the stress response, although their relationship with the HPA axis is inconclusive. More stable HPA axis biomarkers, such as hair samples of cortisol (HC) and dehydroepiandrosterone (HDHEA), would help to clarify the association between these psychological traits and HPA axis functioning. The main aim of this study was to test the relationships between optimism and pessimism and chronic stress biomarkers measured in hair (HC and HDHEA). Additionally, a secondary objective was to explore sex differences in HC and HDHEA levels and their relationship with these psychological traits. We measured optimism, pessimism, and their combination (dispositional optimism) using the Life Orientation Test Revised (LOT-R) and chronic stress biomarkers (HC and HDHEA) in 119 healthy participants (46 men and 73 women) between 56 and 81 years old who belonged to a university program. Regression analyses controlling for perceived stress and BMI indicated that higher dispositional optimism was related to lower HC and HC:HDHEAratio (β = -0.256, p = .008 and β = -0.300, p = .002, respectively). More specifically, higher pessimism was related to higher HC (β = 0.235; p = .012) and HC:HDHEAratio (β = 0.240; p = .011), whereas higher optimism was associated with a lower HC:HDHEAratio (β = -0.205; p = .031). Moderation analyses showed no sex differences. To date, this is the first study to investigate the link between these traits and HC and HDHEA in older people. Our results confirm that positive and negative expectations about the future (i.e. optimism and pessimism) may play an important role in health due to their relationship with the HPA axis. They also strengthen the idea that the negative effects of pessimism have a greater weight than the protective effects of optimism in their relationship with HPA axis regulation.