Shelby Stowe, Colorado School of Mines
Authors: Shelby Stowe MS, Monique LeBourgeois PhD, Cecilia Diniz Behn PhD
2022 AWM Research Symposium
Poster Presentation

A major developmental milestone during early childhood is the consolidation of sleep from a biphasic sleep-wake pattern (afternoon nap and nighttime sleep episodes) to a single monophasic nighttime sleep episode. An advance in the timing of the circadian system is associated with reduced napping behavior, but it is unknown if this advance is a feature of the developing circadian system or altered patterns of light exposure. Using a validated mathematical model of the human circadian pacemaker, we investigated potential mechanisms for producing the circadian phases associated with napping and non-napping light schedules. Extant physiological and behavioral data from 20 children (34.2±2.0 months) were used in this analysis. We found that the model predicted different circadian phases for each pattern of light exposure: both the decrease in afternoon light during the nap and the later bedtimes associated with napping toddlers contributed to the observed differences in circadian phase. In addition, we systematically quantified the effects on phase shifting due to nap duration, timing, and light intensity. We found larger phase delays occurred for longer and earlier naps. Therefore, napping status affects circadian timing due to altered patterns of light exposure. Furthermore, these findings suggest napping status may affect re-entrainment dynamics in toddlers experiencing circadian misalignment (e.g., jet lag).

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