School start times and late screen time exacerbate sleep deprivation in US teenagers

School start times and late screen time exacerbate sleep deprivation in US teenagers
Credit: Pixabay/CC0 Public domain

With the school year underway around the U.S., parents and caregivers are once again faced with the age-old struggle of wrangling groggy kids out of bed in the morning. It can be especially difficult for parents of teenagers and preteens.

Sometimes this is attributed to teenage laziness. A healthy person cannot naturally wake up without an alarm because they aren’t getting the sleep that their brain and bodies need.

That’s because studies show that adolescents need more than nine hours of daily sleep to be physically and mentally healthy.

But chances are that you don’t know any teenagers who get enough sleep. In the U.S., less than 30% of high school students–or those in grades 9 through 12–sleep the recommended amount, according to the Centers for Disease Control and Prevention. Among middle schoolers in grades 6-8, nearly 60% do not get enough sleep at night.

But my laboratory’s research suggests a much higher proportion of teens getting too little sleep.

I am a professor of biology and have been studying sleep and circadian rhythms for more than 30 years. My laboratory at the University of Washington has been researching sleep among teenagers in Seattle for seven years. Our research has found that, just as in other areas of the U.S., high schoolers in Seattle are not getting the amount of sleep they need. Our study objectively measured sleep in 182 high school sophomores and seniors and found only two that slept at least nine hours at night during school days.

Our studies and those of others indicate that three important factors lie behind this lack-of-sleep epidemic: a physiological regulation of sleep that leads to a delayed sleep timing in teens and that is not aligned with early school start times, a lack of morning exposure to daylight and excessive exposure to bright electric light and screens late in the evening.

Teen sleep biology

The time people go to bed, fall asleep and wake up is governed by two main factors in the brain. The first is the so-called “wakefulness monitor”, a physiological timer that increases the need for sleep the longer we stay awake. This is in part the consequence of the accumulation of chemical signals released by neurons, such as adenosine.

Adenosine builds up in the brain while we are awake. This leads to increased sleepiness over time. For example, if a person wakes up at 7 AM, these chemical signals will build up throughout the day until they reach a level that causes them to fall asleep. This is usually in the late evening.

The second factor that drives the sleep/wake cycle is a 24-hour biological clock that tells our brain what times of the day we should be awake and what times we should be sleeping. The hypothalamus is the brain’s biological clock. The clock is composed of neurons that coordinate the brain areas regulating sleep and wakefulness to a 24-hour sleep/wake cycle.

These regulators work in relative independence from one another. But under typical conditions, they are coordinated so that a person with access to electric-powered light would fall asleep in the late evening–between about 10 p.m. to 11 p.m., and wake up in the early morning, around 6 a.m. to 7 a.m.

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Sufficient sleep is key to teen health, but many things prevent adolescents from getting enough of it.

So why do teenagers often want to go to bed later and wake up later than their parents?

It turns out that both the biological clock and the wakefulness tracker conspire to delay sleep. First, adolescents can be awake until later hours before their wakefulness tracker makes them feel sleepy enough to fall sleep.

Second, the biological clock of teenagers is delayed because in some cases it appears to run at a slower pace, and because it responds differently to light cues that reset the clock daily. This combination leads to a sleep cycle that operates a couple of hours later than in an older adult–if an older adult feels the signals to fall asleep around 10 p.m. or 11 p.m., this won’t happen until midnight or later in a teenager.

How school start times contribute

To help find more hours of sleep for teens, one measure that some school districts around the country have taken is to delay the school start time for middle schools and high schools. The American Academy of Pediatrics recommends that schools for this age group should not start before 8: 30 a.m.. Yet the majority of high schools in the U.S start at 8 a.m. or earlier.

Based on the recommendation of sleep experts, the Seattle school district, beginning with the 2016-2017 school year, delayed middle school and high school start times by nearly an hour, from 7: 50 a.m. to 8: 45 a.m. In a study our team conducted after the district enacted the plan, we found that students gained 34 minutes of daily sleep–a huge gain by sleep medicine standards. Additionally, attendance and punctuality of students improved and their median grades increased by 4.5%.

Despite an abundance of research evidence and the advice from virtually all sleep experts in the country, most school districts are still stuck with school start times that promote chronic sleep deprivation in teenagers. The early school starts are further aggravated by daylight saving time–when clocks are set one hour ahead in the springtime. This time shift–one that could become permanent in the U.S. in 2023–exposes teenagers to artificially dark mornings, which exacerbates their naturally delayed sleep timing.

Teaching healthy sleep habits to teens

School start times aside, children must also learn healthy habits that promote adequate sleep.

Getting bright daylight exposure, particularly during the morning, pushes our biological clock to an earlier time. This, in turn, will promote an earlier bedtime and a natural early morning wake time.

In contrast to this, light in the evening, including the light emitted from screens, is highly stimulating for the brain. It inhibits the production of natural signals such as melatonin, a hormone that is produced by the brain’s pineal gland as the night arrives and in response to darkness. Artificial light in the evening can cause biological clocks to delay, which results in a later bedtime and a later wake-up time. So the cycle of having a sleepy, yawning teenager get up for school starts again.

Few schools teach the importance and importance of good sleep habits and time management. Parents and teens are also often unaware of their importance. Chronic sleep deprivation disrupts every physiological process in the body and has been consistently linked to disease, including depression and anxiety, obesity and addictive behavior.

Conversely, sufficient sleep not only helps to reduce physical ailments and improve mental health, but it has also been shown to be fundamental for optimal physical and mental performance.

This article is republished from The Conversation under a Creative Commons license. Read the original article. The Conversation

School start times and late screen time exacerbate sleep deprivation in US teenagers (2022, September 18)
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