How much sleep do I need, and why?

How much sleep do I need, and why?


Most teenagers need between 9 and 9½ hours of sleep each night. Yet surveys show that most teenagers get only 6 to 7 hours. Twenty percent of high schoolers say that they have fallen asleep in class.

If you don't get enough sleep, you may experience symptoms of sleep deprivation. These include:
Falling asleep in class.
Irritability.

Having a hard time waking up in the morning.

Difficulty concentrating.

Depression after prolonged sleep deprivation.
One study looked at the relationship between sleep and grades. The study found that teenagers who got more sleep had more A's and B's, while teens who got less sleep got more C's and D's.

There are many other ways in which the right amount of sleep can keep you healthy. During sleep the body:
Repairs cells: Sleep slows metabolism, heartbeat and breathing rate, which helps the body replenish after daily physical activity.
Releases growth hormones in young adults: While you sleep, a hormone is released that aids the growth of bones, tissues and new red blood cells.

Strengthens your immune and nervous systems.
Sleep is necessary for survival. Experiments have shown that rats who are forced to remain awake die in a little over two weeks. Interestingly, when rats are allowed to sleep but not dream, they also die. Dreams stimulate the brain regions used in learning and help us organize thoughts and images from the day into memories. In dreams, many people seem to work through problems they haven't been able to focus on during the day – ranging from math homework to friendships.

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What is sleep?


People used to think of sleep as an activity where not much happened. Studies show, however, that the brain and body are very active while we sleep.

There are two kinds of sleep: non-rapid eye movement eye movement (NREM) and rapid eye movement (REM) sleep. These two states affect the body and mind in different ways.

NREM Sleep

Most of us, if we are lucky, fall asleep within 10 to 20 minutes of going to bed. Our bodies begin a cycle of sleep. The first four stages are NREM. Stages 1 and 2 are light sleep where we can be awakened easily and contractions of our muscles can be seen. In stages 3 and 4 our brain waves slow and we enter into deep sleep – it is very difficult to wake someone up in this stage. There is no eye movement or muscle activity at this point.

REM Sleep and Dreaming

The fifth stage of sleep occurs normally after about 90 minutes, and is characterized by dreaming and rapid eye movement. No other muscles move during this time. If you have the chance to watch a friend or family member sleep, check to see if their eyes are moving back and forth, like they are watching a movie underneath closed eyelids. If so, they are likely in the middle of a dream.

The cycles of NREM and REM sleep repeat throughout the night. The first period of dreaming only lasts five minutes. REM periods are longer with each subsequent cycle. We typically spend more than two hours each night dreaming.