Bidirectional relationships between sleep and biomarkers of stress and immunity in youth

Insufficient sleep during childhood can lead to physical and mental health issues. In adults, sleep disturbances have been associated with altered levels of stress hormones and inflammatory cytokines, but data in youth is lacking. The aim of this study was to explore relationships between objective measures of sleep and salivary biomarkers in children and adolescents. Participants (N = 55, aged 8-16 years, 53% female) wore an actigraph sleep monitor in their home for seven nights and completed sleep diaries and the School Sleep Habits Survey (SSHS). Participants also donated first waking saliva samples, which were later assayed for alpha-amylase (sAA), cortisol, interleukin (IL)-6, and IL-18. While sAA was not associated with objective sleep it did show a positive association with self-reported sleep disturbance. Morning cortisol levels were associated with objective sleep variables, including minutes spent awake the night before sampling, and sleep efficiency and awakenings the night after sampling. Morning IL-6 was associated with prior night sleep efficiency and minutes spent awake the night after saliva sampling. Likewise, IL-18 levels were associated with sleep duration and sleep onset latency during the nighttime sleep period prior to and after saliva sampling. These results align with other data to indicate objective elements of sleep are related to salivary cortisol, IL-6, and IL-18 in youth. Thus, quality of sleep on the night prior to sampling should be considered when investigating levels of salivary mediators in children.