Adolescents and Circadian Misalignment: Risk Factors for Metabolic Disruption

By: Amrita Rehal

In recent years, sleep disruptions and insufficient sleep have been implicated in the development of a multitude of metabolic disorders.¹ It is becoming clear that enough sleep, and well-timed sleep for that matter, are extremely important in maintaining optimal energy removal and usage from food throughout the 24-hour circadian day. As more attention is turned to disparities in sleep health amongst a variety of populations, the difficulties faced by vulnerable and marginalized populations are being illuminated. One of the most overlooked of these populations is adolescents.

The adolescent transition marks a time of great change for young people, as they undergo puberty and transition into high school, encountering numerous biological and psychological changes. One of these major changes occurs in their sleep habits.² There is a well-established two-process model of sleep regulation that involves a homeostatic Process S which depends on sleep/wake patterns and a circadian Process C that depends on the 24-hour internal clock. Both processes undergo developmental changes during adolescence, as teens experience a circadian phase delay. This means that they exhibit an evening preference that causes them to desire significantly later bed and rise times. A slowing of Process S also occurs in adolescence, causing sleep pressure to build up much slower. Sleep pressure increases as one remains awake and dissipates as one sleeps. Developmental delays to the homeostatic sleep and wake cycle results in a much later sleep onset and the newfound ability to stay awake longer in adolescence. This is because sleep pressure is not as powerful at night for adolescents.³ This biological shift, for which the reasons are not yet well understood, contributes to circadian misalignment in teens. It is defined as a mismatch between one’s sleep/wake schedule and their internal body clock timing.

Adolescents in the United States regularly experience circadian misalignment due to the extremely early high school start times being a huge constraint to their sleep. Recent media articles have come to focus upon these issues more as research in this area is becoming more recognized.⁴ Teens in the U.S. are often waking up between 5:30am and 6:30am to get to school. Although developmental delays to bed and wake times cause adolescents to prefer later sleep and wake times, they are forced have an earlier wake time than their Processes C and S would biologically initiate.² The circadian misalignment that these teens experience has been implicated in mental health problems, emotional dysregulation, poor school attendance and performance, and even physical problems such as metabolic disorders.

The early school start times of adolescents in the U.S. are contributing to circadian misalignment, leading to the metabolic disorder known as insulin resistance. Insulin resistance occurs when cells stop responding to insulin, which causes less blood glucose to be taken up into cells. This results in tonic high levels of blood glucose and excess insulin production. Type 2 diabetes eventually results when the body can no longer keep up with the insulin demands, causing obesity amongst other long-term issues, such as sleep apnea, heart disease, stroke, or heart attack. It has been established that less sleep occurring during a person’s biological night results in correlates of insulin resistance.⁵ Adolescents sleep very little during their biological night and are often awake and sitting in classrooms during it.

It remains of dire importance to examine potential treatments or interventions to improve sleep quality in adolescents. These could include policy changes to delay school start times and educational programs to improve sleep hygiene.⁴ Many great research labs are focusing on the widespread effects of ill-timed and poor sleep habits.^1,6 Hopefully, soon, policy makers and researchers can work hand-in-hand to establish better guidelines for vulnerable populations in the U.S., helping improve sleep timing for our youth so they aren’t vulnerable to metabolic disorders such as insulin resistance.

Works Cited:

(1) Fishbein, A. B., Knutson, K. L., & Zee, P. C. (2021). Circadian disruption and human health. The Journal of clinical investigation, 131(19).

(2) Crowley, S. J., Acebo, C., & Carskadon, M. A. (2007). Sleep, circadian rhythms, and delayed phase in adolescence. Sleep medicine, 8(6), 602-612.

(3) Crowley, S. J., Wolfson, A. R., Tarokh, L., & Carskadon, M. A. (2018). An update on adolescent sleep: New evidence informing the perfect storm model. Journal of adolescence, 67, 55-65.

(4) Kinney, M., & Hopkins, K. (2023, February 28). Adjusting to later school start times is good for overall Adolescent Health. Courier Journal. Retrieved March 3, 2023, from https://www.courier-journal.com/story/opinion/2023/02/28/why-adjusting-to-later-school-start-times-is-better-adolescent-health/69950023007/

(5) Simon, S. L., Behn, C. D., Cree-Green, M., Kaar, J. L., Pyle, L., Hawkins, S. M., ... & Nadeau, K. J. (2019). Too late and not enough: school year sleep duration, timing, and circadian misalignment are associated with reduced insulin sensitivity in adolescents with overweight/obesity. The Journal of pediatrics, 205, 257-264.

(6) Poe, A. R., Zhu, L., McClanahan, P. D., Szuperak, M., Anafi, R. C., Thum, A. S., ... & Kayser, M. S. (2022). Developmental emergence of sleep rhythms enables long-term memory capabilities in Drosophila. bioRxiv, 2022-02.