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Treatment and Care for Sleep Disorders
What happens in our body when we sleep?

What happens to our body and how does it happen every time we get a bit of shut eye? Sleep happens in a recurring cycle of 90 to 110 minutes and is divided into two categories: non-REM (which is further split into four stages) and REM sleep.

What is Non-REM sleep

Stage one: Light Sleep

During the first stage of sleep, we're half awake and half asleep. Our muscle activity slows down and slight twitching may occur. This is a period of light sleep, meaning we can be awakened easily at this stage.

Stage two: True Sleep

Within ten minutes of light sleep, we enter stage two, which lasts around 20 minutes. The breathing pattern and heart rate start to slow down. This period accounts for the largest part of human sleep.

Stages three and four: Deep Sleep

During stage three, the brain begins to produce delta waves, a type of wave that is large (high amplitude) and slow (low frequency). Breathing and heart rate are at their lowest levels.

Stage four is characterized by rhythmic breathing and limited muscle activity. If we are awakened during deep sleep we do not adjust immediately and often feel groggy and disoriented for several minutes after waking up. Some children experience bed wetting, night terror , or sleepwalking during this stage. We encourage you to visit a Sleep Specialist if you or your child experiences any of these symptom.

Closed eye What is REM sleep

The first rapid eye movement (REM) period usually begins about 70 to 90 minutes after we fall asleep. We have around three to five REM episodes a night.

Although we are not conscious, the brain is very active - often more so than when we are awake. This is the period when most dreams occur. Our eyes dart around (hence the name), our breathing rate and blood pressure rise. However, our bodies are effectively paralyses, said to be nature's way of preventing us from acting out our dreams.

After REM sleep, the whole cycle begins again.

How much sleep do other species may need?

Animals require varied amounts of sleep:

Species Average total sleep time per day
Python - 18 hrs
Tiger - 15.8 hrs
Cat - 12.1 hrs
Chimpanzee - 9.7 hrs
Sheep - 3.8 hrs
African elephant - 3.3 hrs
Giraffe - 1.9 hr

Shahriar Shahzeidi, M.D. FAAP, FCCP, FAASM
Medical Director
Pediatrician-in-Chief
Fellow of the College of Chest Physicians
Fellow of the American Academy of Pediatrics
Fellow of the American Academy of Sleep Medicine
AASP
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GHI In the News
Washington Post / Shahzeidi, GHI
Miami Herald Article

Related Links
• National Sleep Foundation - Website
• American Academy of Sleep Medicine - Website
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