B2-10 · Why We Sleep – and Why Teenagers Don’t

Why We Sleep – and Why Teenagers Don't

We spend about a third of our lives asleep. For centuries, people saw sleep as wasted time – a pause in which nothing important happened. Thomas Edison, the inventor of the practical light bulb, called it "a heritage from our cave days" and was proud of sleeping very little. Modern science says Edison was wrong. Sleep is not a pause; it is one of the busiest times for the brain.

What happens at night

During the night, we go through several cycles of sleep, each lasting about 90 minutes. In deep sleep, the body repairs muscles and the immune system gets stronger. In REM sleep (named after the rapid eye movements that happen during it), we have most of our vivid dreams. REM sleep is believed to help us process emotions and make creative connections between ideas.

One of the most important jobs of sleep is to organize memory. While we sleep, the brain replays what we learned during the day and moves it from short-term to long-term storage. Students who sleep after learning new vocabulary remember significantly more the next day than students who stay awake. Scientists have also discovered that the brain uses sleep to clean itself: a system of fluid washes away waste products that build up during the day.

The teenage clock

If you find it hard to fall asleep before midnight and even harder to get up for a 7:30 class, you are not lazy. During puberty, the body clock moves later. The brain starts releasing melatonin, the hormone that makes us sleepy, up to two hours later than in children or adults. As a result, a typical teenager is biologically ready to sleep at around 11 p.m. and wake up at around 8 a.m.

Unfortunately, most schools start early. Experts recommend that teenagers sleep eight to ten hours a night, but surveys suggest that most high school students get much less on school nights. Some American school districts have tested later start times. When high schools in Seattle moved their first class from 7:50 to 8:45 in 2016, students slept on average more than half an hour longer, and their grades and attendance improved.

The screen problem

Our habits make the situation worse. The blue light from phones and laptops is thought to delay melatonin, and – perhaps more importantly – endless videos and messages keep the brain alert. Many teenagers sleep with their phone next to the bed, and a single notification at 2 a.m. can interrupt a sleep cycle.

Missing sleep has real consequences. People who sleep too little have slower reactions, worse concentration and less control over their emotions. Driving after being awake for about 18 hours has been compared to driving with a blood alcohol level that is illegal in many countries. Over a long time, poor sleep is linked to weight gain, depression and a weaker immune system.

How to sleep better

Sleep researchers usually give similar advice. Go to bed and get up at roughly the same time, even on weekends. Keep your bedroom cool, dark and quiet. Avoid caffeine in the afternoon – energy drinks included. And put your phone away at least half an hour before bed, ideally outside the bedroom.

It may sound boring, but a good night's sleep is probably the cheapest and most effective way to learn better, feel better and look better. Edison might have invented the light bulb, but he would probably have been even more productive if he had switched it off.