Understanding sleep-wake behavior and sleep disorders in children: the value of a model

Abstract

Purpose of review: Sleep-wake problems such as night wakings, excessive crying, or difficulties in falling asleep are frequent behavioral issues during childhood. Maturational changes in sleep and circadian regulation likely contribute to the development and maintenance of such problems. This review highlights the recent research examining bioregulatory sleep mechanisms during development and provides a model for predicting sleep-wake behavior in young humans.

Recent findings: Findings demonstrate that circadian and sleep homeostatic processes exhibit maturational changes during the first two decades of life. The developing interaction of both processes may be a key determinant of sleep-wake and crying behavior in infancy. Evidence shows that the dynamics of sleep homeostatic processes slow down in the course of childhood (i.e., sleep pressure accumulates more slowly with increasing age) enabling children to be awake for consolidated periods during the day. Another current topic is the adolescent sleep phase delay, which appears to be driven primarily by maturational changes in sleep homeostatic and circadian processes.

Summary: The two-process model of sleep regulation is a valuable framework for understanding and predicting sleep-wake behavior in young humans. Such knowledge is important for improving anticipatory guidance, parental education, and patient care, as well as for developing appropriate social policies.

Figure 1. Two-process model of sleep regulation

Homeostatic and circadian modulation of sleep pressure during the day and at night. The circadian process is a clock-like process, whereas the homeostatic sleep–wake dependent process is an hourglass process. Data from Achermann and Borbély [11]. W indicates the wake period and S sleep.

Figure 2. Conceptual model of sleep–wake regulation in early infancy

Negative upper arrows represent increasing sleep pressure (plotted upside down), while positive lower arrows indicate increasing circadian drive. Black bars represent sleep episodes. Adapted from [17]. The ability of the infant to decrease sleep pressure during the night counteracts the drop in circadian alertness during the night for maintaining a consolidated nocturnal sleep episode. The increase of sleep pressure during the day opposes the circadian alerting signal in the early evening for sustaining a balanced vigilance state during the day.

Figure 3. The sleep homeostatic process as a function of age

Proposed developmental changes in accumulation of sleep pressure as a function of time since waking depicted for different ages. Sleep pressure accumulates more slowly during the day with increasing age.