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SummaryRecent evidence suggests that poor sleep is a potential pathway underlying the association between stressful experiences and the diurnal cortisol profile. However, existing findings are largely limited to adults. The present study examines whether poor sleep (duration, quality) mediates the relation between stressful experiences and the diurnal cortisol profile in children and adolescents. Children and adolescents (N = 220, M age = 12.62) provided six saliva samples over two days to derive cortisol indices (bedtime, AUC AG , AUC TG , slope MAX ). Perceived stress, stressful life events, self-reported sleep duration, and sleep quality were measured. Using bootstrapping analyses, sleep quality mediated the relation between perceived stress and AUC TG (R2 = 0.10, F(7, 212) = 3.55, p = .001; 95% BCI[0.09, 1.15]), as well as the relation between stressful life events and AUC TG (R2 = 0.11, F(7, 212) = 3.69, p = .001; 95% BCI[0.40, 3.82]).These mediation models remained significant after adjusting for sleep duration, suggesting that poor sleep quality underlies the association between stressful experiences and the diurnal cortisol profile in children and adolescents. Longitudinal data combined with objectively-measured sleep is essential to further disentangle the complex association between sleep and stress. KeywordsSleep; Cortisol; Stressful life events; Perceived stress; Child; Adolescent Stress is known to alter cortisol secretion. Exposure to acute laboratory-induced stressors elicits transient increases in cortisol level (Dickerson and Kemeny, 2004). Naturally occurring stressful experiences, including perceived stress and stressful life events, have also been associated with a disrupted diurnal cortisol profile. Adults who report greater perceived stress (i.e., nonspecific, subjective appraised stress, Cohen et al., 1995) CIHR Author ManuscriptCIHR Author Manuscript CIHR Author Manuscript awakening response, total cortisol level, and flatter diurnal slopes (Miller et al., 2007;Pruessner et al., 1999;Schulz et al., 1998). Greater stressful life events (e.g., unemployment, divorce) are associated with higher morning and evening cortisol levels and flatter diurnal slopes (Miller et al., 2007). Similar findings have been established in both children and adolescents (hereafter referred to as "youth" for parsimony). Youth who report greater stressful life events (e.g., family conflict, academic stress) have a higher cortisol awakening response and elevated afternoon cortisol levels than their less stressed counterparts (Gustafsson et al., 2010;Wolf et al., 2008). While there is convincing evidence that stressful experiences disrupt the diurnal cortisol profile, the potential pathways underlying this association remain unclear.Sleep is one plausible pathway by which stressful experiences disrupt the diurnal cortisol profile. The sleep-wake cycle has a close, temporal association with diurnal cortisol secretion. Nocturnal sleep onset reliably exerts an inhibitory effect on cortisol secretion (Van Cauter et al.,...

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Rationale/statement of the problem : In adults, there is a robust, immediate effect of sleep on the diurnal cortisol profile. Shorter sleep duration and poorer sleep quality are associated with greater awakening response, flatter diurnal slope, and higher evening cortisol levels. Because of methodological limitations, this relation is less well-established in children and adolescents. Specifically, the use of single cortisol samples and sampling at unconventional times limit the generalizability of these findings. This study examines the influence of sleep duration, sleep quality, and daytime sleepiness on the diurnal cortisol profile in children and adolescents. Methods : Children and adolescents aged 8–18 (N = 227, M = 12.61, SD = 2.04, 45.8% female) participated in the Healthy Heart Project at Concordia University. Children and adolescents rated their sleep quality on a 1–10 scale (1 = poor, 10 = excellent) and completed the Pediatric Daytime Sleepiness Scale. Parents completed the Child's Sleep Habits Questionnaire and reported their children's bedtime and waketime to derive sleep duration. Six saliva samples were collected over 2 days. Single sample (bedtime, maximum) and aggregate measures (AUCAG, AUCI, AUCTG, diurnal slope) of the diurnal cortisol profile were derived. Results : After controlling for age and day of the week, higher bedtime cortisol was associated with shorter sleep duration (r= − 0.17, p=.01), poorer sleep quality (r= − 0.19, p=01), and greater child-report daytime sleepiness (r=0.16, p=.02). Higher AUCTG was associated with poorer sleep quality (r= − 0.15, p=.02); higher AUCI was related to greater child-report daytime sleepiness (r=0.14, p=.03). Parent-report sleep problems and daytime sleepiness were not associated with any cortisol measure. Maximum sample, AUCAG, and diurnal slope were not related to any sleep measure. Conclusion : Poorer sleep quality, greater daytime sleepiness, and shorter sleep duration were related to higher bedtime cortisol. Poorer sleep quality and greater daytime sleepiness were associated with higher AUCTG and AUCI, respectively. While child-report measures of sleep were associated with cortisol, parent-report measures were not. Current findings offer insight into possible pathways linking sleep and health. Future studies should further elucidate this association by examining objective measures of sleep