Effects of school start time in the morning on sleep and health of adolescents

Biological sleep regulation delays progressively throughout adolescence. Therefore, adolescents fall asleep later and later in the night. Because school starts early in the morning, later bedtimes cannot be compensate for with correspondingly later wake-up times. Consequently, most adolescents accumulate a growing sleep deficit throughout the school week. This is problematic because sleep is closely linked to mental and physical health, cognitive abilities, and brain development. International studies have shown positive effects of later school start times: students wake up later in the morning but still go to bed at roughly the same time, resulting in increased total sleep duration, improved well-being, and better academic performance. We are investigating in various projects how morning school start times affect adolescents and how they can be optimized. The projects emcompass both basic research and scientific evaluation of school development initiatives in practice.

Completed projects:

• School start time preference of students and teachers: Online surveys conducted at 17 high schools in the Canton of Zurich revealed that both students and teachers would endorse later morning school start times. Students reported a preferred start time of 08:38, which corresponds to a 55-minute shift from the actual start time. Teachers preferred a start time of 08:00. The more problematic the individual sleep behavior (i.e., the less compatible it was with early start times), the stronger the reported preference for later school start times. Further details can be found in our publications: https://onlinelibrary.wiley.com/doi/full/10.1111/jsr.13401 & https://onlinelibrary.wiley.com/doi/full/10.1111/jsr.13534
• Effects of pandemic school closures on sleep and health of adolescents: During the Covid-19 pandemic, schools had to close temporarily and students were taught exclusively through homeschooling. As a result, adolescents no longer had to commute, and many had greater flexibility in structuring their school day. We repeated our surveys at the same high schools during the pandemic school closures in 2020 and one year later in 2021, when schools had reopened but most pandemic restrictions were still in place. The results showed that during the school closures, students woke up significantly later on school days while maintaining similar bedtimes, thereby gaining over an hour of additional sleep. Furthermore, students reported better health-related quality of life and reduced substance use. After the closures ended, these positive effects disappeared, and the burden of the pandemic on adolescents became (even) more apparent. Further details can be found in our publications: https://jamanetwork.com/journals/jamanetworkopen/fullarticle/2787630 & https://www.mdpi.com/1660-4601/19/9/5078

Ongoing projects:

• Effects of flexible school start times in the morning: A secondary school in Gossau, St. Gallen (Oberstufe Gossau), introduced a new school model involving flexible start times in the morning. Students can now choose whether to attend their first lesson at 7:20 AM or start their school day later, earliest at 8:30 AM. We investigated the impact of this model on sleep, well-being, and academic performance. One year after the implementation, the results showed that on most school days, students chose the later start, woke up later, and slept an additional 45 minutes in total. Furthermore, sleep onset problems were less frequent, fewer students reported clinically relevant low scores in health-related quality of life, and results in the Stellwerk tests improved. More details can be found in our publication: https://www.sciencedirect.com/science/article/pii/S1054139X26000133 or in the news report: https://www.srf.ch/news/schweiz/ausgeschlafen-lernen-flexibler-schulstart-verbessert-schlaf-und-leistungenTo examine long-term effects, we repeated the survey two years after the flexible model was introduced and are currently analyzing the results.

Team Sleep and School:
Dr. Joëlle Albrecht,
Prof. Dr. Reto Huber
Prof. Dr. Oskar Jenni
Ehemalige Projektmitarbeitende: PD Dr. Helene Werner, Alessa Risch, Anika Sander, Daniel Janisch, Mei Ling Yaw, Natacha Widmer, Noa Rieger

Institution:
Abteilung Entwicklungspädiatrie, Universitäts-Kinderspital Zürich, Universität Zürich

We are regularly looking for interns, bachelor and master students. If you are interested in our projects, feel free to contact us at  joelle.albrecht@kispi.uzh.ch.