Biological processes related to positive development after preterm birth: the interplay between sleep, hypothalamic-pituitary-adrenal axis activity, and autonomic functioning, and the role of parental insomnia symptoms

Abstract

Biological processes, including sleep, the hypothalamic-pituitary-adrenocortical (HPA) axis, and the autonomic nervous system (ANS), play an important role in positive development across the life-span. They are highly susceptible to early life experiences such as very preterm (VP) birth and to concurrent environmental factors such as parental sleep. Yet, research examining sleep, HPA axis activity, and ANS functioning in children and adolescents is rare. Therefore, the goal of this cumulative dissertation containing three studies is (a) to extend knowledge of the interplay between sleep, HPA axis activity, and ANS functioning during childhood and adolescence, (b) to examine the role of VP birth in these biological processes, and (c) to test whether parental insomnia symptoms are related to their children’s sleep as well as to parental perception of children’s sleep-related behavior. The samples included in the studies of this dissertation derived from the second wave of the Basel Study of Preterm Children investigating VP and full-term (FT) children and adolescents. Findings from Study 1 (Maurer et al., 2016) showed an association between elevated post-awakening HPA axis activity and a later sleep onset time, shorter sleep duration, and shorter rapid eye movement latency across the whole sample. Additionally, Study 2 (Urfer-Maurer et al., 2018) showed that predominant sympathetic activity of the ANS at rest and during different sleep stages was related to increased post-awakening HPA axis activity across the whole sample. Further, Study 1 showed that VP children had an earlier sleep onset time and lower HPA axis activity compared to FT children. Mediation analyses showed that earlier sleep onset time partially accounted for lower post-awakening HPA axis activity in VP children. Moreover, Study 2 showed that VP children had a dominance of parasympathetic over sympathetic activity of the ANS when awake and during stage 2 sleep. The results of Study 3 (Urfer-Maurer et al., 2017) revealed that maternal but not paternal insomnia symptoms were related to less restorative sleep in children. Finally, parental insomnia symptoms were related to parents’ reports of their children’s sleep-related behavior, and maternal insomnia symptoms were additionally related to paternal reports of sleep-related behavior in children. Findings of the present dissertation highlight the important role VP birth plays in altered development of biological processes, especially HPA axis activity during childhood and adolescence. Additionally, they emphasize that parental sleep difficulties may affect the sleep of their own children as well as how they perceive their children’s sleep. This dissertation outlines the practical implications of these results for the design of new treatments to foster positive development associated with sleep, HPA axis activity, and ANS functioning.