Objective: To examine whether dysregulation of the hypothalamic-pituitary-adrenal (HPA) axis associated with disadvantaged social position in working populations also occurs in older age groups.
Methods: This study examines the association of several indicators of social position with two measures of cortisol secretion, a product of the HPA axis. We examined the cortisol awakening response (CAR), and slope of the decline in cortisol secretion across the day. We examine whether the association is mediated by behavioral, psychosocial, and biological factors in 3992 participants of phase 7 (2002-2004) of the Whitehall II study, who provided six salivary cortisol samples across the day.
Results: In this older cohort (mean age = 61 years; range = 50-74 years), lowest social position (assessed by current or previous occupational grade and wealth) was associated with a flatter slope in the decline in cortisol secretion. For example, over the course of the day, men in the lowest employment grades had a reduction in their cortisol by 0.125 (nmol/L/h), which was a shallower slope than those in the high grades (-0.129 nmol/L/h). The difference in slopes by employment grade among men, but not women, was statistically significant (p = .003). The difference in slopes was explained primarily by poor health and sleep behaviors, although financial insecurity also played a role. No effects were apparent with the CAR or other measures of social position.
Conclusions: In men, poorer health and sleep behaviors (primarily smoking and short sleep duration), and financial insecurity mediate the impact of occupational status and wealth on cortisol secretion.