Julian CL Lai
The Hypothalamic–Pituitary–Adrenal (HPA) axis is crucial for homeostatic and allostatic adjustments to internal and external challenges. However, how aging affects this neuroendocrine axis is still incompletely understood. Being the end-product of the HPA axis, cortisol has been extensively studied for the last two decades because an increased cortisol response to psychosocial challenge has been hypothesized to be a risk factor for developing a number of age-related disorders in humans. This hypothesis has been addressed by separate lines of research focusing on the impact of acute laboratory stressors and chronic natural stressors on cortisol secretion in the elderly. This paper summarizes major findings generated by the aforementioned lines of research with a focus on studies examining salivary cortisol. It is concluded that although age does not have a consistent effect on cortisol response to acute laboratory stressors, evidence supporting an age effect on basal cortisol secretion is emerging. Moreover, the age-cortisol relationship is modulated by chronic stress and other psychosocial factors. Further research is warranted to throw more light on these preliminary findings.