Association of Infant Sleep with Chronic and Day-to-day Physiological Stress

• In Event: 1-149 - Sleep in High-Risk Young Children: Disparities, Behavioral Correlates, and Intervention Results

Integrative Statement

Introduction
Sleep and physiological stress are two domains of self-regulation that are intertwined in early childhood and susceptible to early perturbations. Infants from low-income households are at increased risk of dysregulation of both sleep and physiological stress, contributing to long-term socioeconomic health disparities. Over time, sleep problems may lead to higher cumulative exposure to the stress hormone cortisol, resulting in increased health risks. To test whether sleep has implications for chronic physiological stress as early as infancy, this study examines actigraphy-derived sleep in relation to hair cortisol. Both sleep and cortisol levels vary from day to day, and temporal dependencies between daily sleep and diurnal cortisol regulation are not well understood. Thus, this study investigates how sleep onset and nighttime sleep duration relate to salivary cortisol the next day, and how bedtime cortisol relates to sleep onset on the same night. To understand sociocontextual contributions, we also examined how the sleep environment varied by sociodemographic risk, and implications of the sleep environment for infant sleep onset and nighttime sleep duration.

Methods
One-year-old infants (N=84, 43 female, M=12.24 months) provided hair samples to index hair cortisol concentration. Infant salivary cortisol was sampled at wake, afternoon and bedtime for 3 days, yielding area under the curve (AUC) from waking to bedtime, reflecting cortisol exposure across the day. On the 3 nights preceding salivary cortisol sampling, infant sleep onset and nighttime sleep duration were recorded using actigraphy. Infant bedtime routine, cosleeping, and household chaos were obtained from parent report. Income-to-needs ratio (ITN) was computed from parent-reported family income and federal poverty guidelines. Parental positive speech was coded based on tone and content from parent-infant free play as an index of parental sensitivity.

Results
Infants with higher hair cortisol, indexing higher cumulative stress, had shorter nighttime sleep duration (r=-.35, p<.01) and later sleep onset (r=.48, p<.01). Sleep was temporally related to day-to-day cortisol, such that later sleep onset (r=.18, p=.02) and shorter nighttime sleep duration (r=-.19, p=.01) related to higher salivary AUC the next day. Higher bedtime cortisol related to later sleep onset the same night (r=.22, p=.01). Infant sleep was sensitive to sociodemographic risks, such that less parental positive speech, lower ITN and more chaotic homes related to later sleep onset and shorter nighttime sleep (Table 1). Co-sleeping and presence of a parent during bedtime were more common in lower income and more chaotic households and related to poorer infant sleep (Table 2).

Discussion
Findings suggest that infants with lower family income, less sensitive parenting and chaotic homes are at risk for poor sleep health. Results indicate that infant sleep not only has implications for long-term physiological stress exposure and the related wear and tear on the body, but also interacts with cortisol levels on a day-to-day basis. Synchronously well-regulated sleep and physiological stress systems are critical for better health outcomes. Future research should examine if interventions to improve infant sleep would contribute to improved cortisol regulation as well.

Authors

• Charu Tara Tuladhar, Boston University
  Presenting Author

• Jerrold S. Meyer, University of Massachusetts Amherst
  Non-Presenting Author

• Amanda Tarullo, Boston University
  Non-Presenting Author