Exposure to poverty since birth and cortisol awakening response in 10-year old children

Background: Exposure to childhood poverty is associated with health problems in children and poor health in adulthood, irrespective of poverty exposure during adulthood. Stress pathways have been suggested as one mechanism. The cortisol awakening response (CAR), a biological response to stress, occurs 30 to 45 minutes after awakening. It is elevated with mild stress, and blunted with more severe stress. Most studies linking altered cortisol to early life poverty are cross-sectional. Objective: To examine, longitudinally, in 10-year old children, the relationship between CAR and the timing of exposure to poverty since birth. Methods: Data were drawn from the birth cohort of the Quebec Longitudinal Study of Child Development. CAR was measured in 10-year old children (n=445) and examined in associations with poverty exposures including: low income, socioeconomic status and social welfare. Salivary cortisol was measured from samples taken upon awakening and 30-45 minutes later on two weekdays. Timing of exposure was assessed: (i) exclusively before 5 years of age; (ii) exclusively between 5 and 10 years; and (iii) both before and after 5 years of age. Results: Children living with social welfare prior to age 5 years had blunted CAR [mean log CAR=-1.44; (95%CI: -0.044; -2.05)] compared to children never exposed [mean log CAR=-1.07; (95%CI: 0.07; -2.07), p<0.01]. Conclusion: Early exposure to severe poverty appears long-lasting in predicting cortisol dysregulation several years after exposure. Cortisol reactivity is a primary mediator of physical and psychological health. These findings support public health interventions to reduce poverty and its impact in vulnerable families.