Psychosocial stress, hypothalamic pituitary adrenal (HPA) axis function, and cardiometabolic health
This dissertation examines the contribution of various psychological and social stressors to indicators of cardiovascular and metabolic function and disease. It also investigates the role of altered hypothalamic pituitary adrenal (HPA) axis activity as a mechanism by which psychosocial stress may influence cardiometabolic health. Grounded in the framework of the allostatic load model, studies 1-3 build on each other to assess the interplay between various types of stress, HPA axis indicators, and cardiometabolic health outcomes among diverse populations. Study 1 examines the association of perceived everyday discrimination and hair cortisol concentration, a stable indicator of retrospective cortisol output indexed over several months. The analyses focus on racial group differences, finding that perceived discrimination scores were associated with elevated hair cortisol concentration for African American adults but not White adults. Given that both groups reported similar discrimination frequency scores, this finding suggests that more qualitative characteristics of discrimination may be particularly salient to HPA axis output among African Americans. Study 2 moves one step past the stress-HPA axis association by examining the role that elevated HPA axis activity plays in the association between perceived stress and metabolic syndrome severity. This study found that psychological resilience protected against the association of elevated perceived stress with increased metabolic syndrome severity via elevated hair cortisol concentration. Study 3 uses the same resilience-based framework as study 2, but does so in a national longitudinal cohort of U.S. adults. Using daily diary entries and salivary cortisol analysis, this study examines unique effects of daily stressor frequency and severity on cardiovascular and metabolic disease prevalence 5-8 years later. Study 3 also tests whether flattened diurnal salivary cortisol slopes mediator effects of stressor frequency and severity on cardiometabolic conditions, and examines a latent resilience resources variable as a potential buffer of the daily stress-cardiometabolic disease relationship. Findings indicate that greater perceived stressor severity and flattened diurnal cortisol slopes predict greater cardiometabolic disease prevalence later in life. Taken together, this collection of studies provides evidence supporting the contribution of greater psychosocial stress to impaired cardiovascular and metabolic health, and suggests that the HPA axis plays a significant role.