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Blog Feature

By: AAST Associate Editor on March 11th, 2022

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Delaying the Bell: The Impact of COVID-19 School Closures on Adolescent Sleep

Start School Later Initiative | COVID-19 | adolescent sleep

It would be an understatement to say that schools, teachers and students have been under immense stress during COVID-19 — turning on a dime to online learning, experiencing isolation and facing a lack of educational support and personal protective equipment (PPE) have only been a few of the challenges. However, recent research shows that increased adolescent sleep duration has proven to be a silver lining thanks to school closures that occurred at the start of the pandemic. Around the world, school closures and schedule changes in response to COVID-19 have also proven that schools are capable of changing their schedules — for the benefit of public health — which means that delaying school start times is possible.

Sleep and the Adolescent Health Paradox

During adolescence, one reaches a peak stage of health and cognitive function; however, at this age, there are sharp increases of morbidity and mortality. This is referred to as the adolescent health paradox. Some negative habits may be introduced and reinforced at this time, including illicit substance use and abuse. Moreover, risk-taking behavior increases in adolescents as does the likelihood of developing mental health conditions that could persist into adulthood.

Many of these issues relate to adolescents’ executive functioning deficits — impaired judgement, impulsiveness, lack of motivation — all of which worsen with lack of sleep. Teenagers ages 13-18 should be sleeping 8 to 10 hours per night; however, two thirds of teens are sleeping less than 7 hours per night. Many factors contribute to the lack of sleep in teens, including an increase in academic workload, demanding extracurricular activities, heightened social activity and the notoriously early school start times.

School Start Times, Adolescent Sleep and Performance

Secondary school start times began to shift at the end of the 20th century from 8:30-9 a.m. to 8 a.m. and in some cases as early as 7:30 a.m. Despite the American Academy of Pediatrics recommending that secondary schools start no earlier than 8:30 a.m. and studies proving school start times are the leading modifiable factor in helping teens achieve adequate sleep, over 80% of school start times occur before 8:30 a.m.

There are both behavioral and biologic factors in adolescent sleep-wake patterns that make starting later advantageous to adolescent cognitive and physical welfare. Bioregulatory factors in adolescents for example favor delays in both falling asleep and waking up, and exposure to blue light at night is a habitual factor of the modern age that effects the sleep-wake cycle. Additionally, humans need both adequate and quality sleep in order to consolidate information and, in turn, learn. Students who receive less than eight hours of sleep per night are unable to learn at their highest potential as their capacity to consolidate information is compromised.

There are several studies that demonstrate that school schedules that match students’ circadian rhythms allow students perform better academically. And conversely, studies suggest that schools with earlier start times have inferior academic achievement. Having later start times has proven to be as effective in increasing student achievement as having a third of the students in a class.

Impact of COVID-19 School Closures and Reopening on Adolescent Sleep

Sleep duration in teens has been decreasing over the last 20 years. But in the early months of the COVID-19 pandemic, young learners around the world began to report they were able to sleep the recommended amount of time for their age each night. In a study conducted on over 3,000 adolescent students in Shanghai, students reported getting, on average, 8.9 hours of sleep during lockdown as opposed to 7.8 hours after schools reopened. Over 85% of students in the study reported an increase in sleep duration during lockdown and the average waking time was delayed by 2.9 hours.

The findings of a study conducted throughout 35 states in the U.S. on 590 teenagers in grades six through 12 during lockdown were not dissimilar: participants reported waking up 2.1-2.9 hours later during remote learning due to the lockdown. The students’ mean sleeping times were between 7.9 and 8.7 hours. With delayed waking times, most students were able to achieve the daily recommended amount of sleep.

In a study conducted in Zurich, comparing pre-pandemic data (May-July 2017) to pandemic-era data (May-June 2020) from 8,972 high school students, students slept on average 75 minutes longer on school days. They also consumed less caffeine and alcohol than before the pandemic. The students’ health-related quality of life, measured by the KIDSCREEN-10 questionnaire, also improved. This information is not to say that students didn’t experience other mental health issues during the pandemic due to isolation and increased stress, but that increased sleep could be a contributing factor to increases in quality of life.


The global lockdown in 2020 demonstrated to the world that schools can be adaptive. Schedules, including school start times are impermanent, as are commuting patterns along with how we work, learn and interact with one another. Communities, cities and countries are also adaptive. With research that supports the benefits adolescents could receive from delaying school start times to 8:30 a.m., there is no better time to urge decision makers on the local government and school district levels to opt for later start times.

Learn More About Teens and Sleep on the AAST Blog