Development of Circadian Regulation and its Implications in Future Health

The adult sleep-wake cycle is regulated by our circadian rhythms, which reflect physiological changes over a 24-hour period. In infants, however, sleep is not yet regulated by these rhythms and is scattered throughout the day (Poe et al., 2022). Poe et al. examined when the development of these rhythms occurred using the model organism Drosophila melanogaster by observing the sleep rhythms of flies at different stages of development. They found that sleep activity became circadian dependent between the L2 and L3 instar larvae stage and suggest that unchecked arousal is a ground state for state changes before this development. The major hypothesis that Poe et al. suggest for this delay in development is that metabolic and nutritional demands are more important in early life, therefore it might be advantageous for the sleep-wake cycle to be non-cyclical for the first stages of life. 

Recent studies have examined the implications of circadian rhythm development in human infants as well. In the article “Development of sleep–wake rhythms during the first year of age”, it was found that infants with slower development of sleep-wake cycles slept more hours during the day, had a later sleep-wake rhythm, took longer to get to sleep, and were awake longer during the night” (Paavonen et al., 2020). These findings are important because it indicates that proper development of the circadian system is crucial to infant sleep quality and quantity. Further, Paavonen et al. suggest that such developmental delays could be connected to sleeping problems which can lead to further sleep disorders later in life.  

Poe et al.’s study identifying the developmental timing of circadian regulation provides background information and identifies a hypothesis as to why circadian regulation doesn’t develop at birth. This information allows us to draw conclusions in regard to the human infant study. Paayonen et al.’s study has the potential to help identify criteria for circadian rhythm dysfunction problems later in life and suggests that a simple way to help improve infant sleep is to adjust to age-appropriate sleep-wake rhythms by paying attention to the timing of naps and maintaining consistent rhythms.

References 

Paavonen, E. J., Morales-Muñoz, I., Pölkki, P., Paunio, T., Porkka-Heiskanen, T., Kylliäinen, A., Partonen, T., & Saarenpää-Heikkilä, O. (2020). Development of sleep-wake rhythms during the first year of age. Journal of sleep research, 29(3), e12918. https://doi.org/10.1111/jsr.12918 

Poe, A. R., Zhu, L., McClanahan, P. D., Szuperak, M., Anafi, R. C., Thum, A. S., Cavanaugh, D. J., & Kayser, M. S. (2022). Developmental emergence of sleep rhythms enables long-term memory capabilities in Drosophila [Preprint]. Neuroscience. https://doi.org/10.1101/2022.02.03.479025