Silvia’s Corner is written by Silvia Hafliger, MD, assistant professor of psychiatry. In her posts, Dr. Hafliger will discuss a wide range of mental health topics and provide useful information to patients and their families.

Silvia's Corner

The Mystery of Sleep — Part 1

Many of us take sleep for granted. However, statistics show that approximately 100 million Americans suffer from occasional insomnia, 30 million toss and turn at least 3 nights a week (women more than men) and 10 million seek advice from a medical doctor for persistent insomnia.

Why do we need sleep?
Sleep is necessary for the body and brain to recover. All animals sleep, including dolphins who must come up for air every few minutes. Dolphins sleep with one half of the brain at a time, while the other side is awake to swim and watch for predators. Sleep deprived rats will lose weight despite eating, become weak and debilitated, are unable to regulate body temperature, suffer internal hemorrhages and even die. In 1963, a 17 year old boy stayed awake for 11 days, the longest all-nighter ever recorded. He became delirious, hallucinatory and paranoid but was able to fully recover once he was able to sleep.

How much sleep do we need?
The good news is that our sleep requirements are different. On average, we need about 7-8 hours per night. However, two out of 10 people need less than 6 hours of sleep, and one out of 10 people need more than 9 hours. Our sleep requirements also change as we age. Newborns sleep about 16 hours a day, but by age 6 children only sleep about 11 hours. As we grow older, we experience less deep sleep and more interruptions.

What are the sleep stages?
There are 3 sleep stages: awake, non-rapid eye movement (NREM) sleep and rapid eye movement (REM) sleep. 75% of our sleep is NREM sleep, or recovery sleep, while 25% is REM sleep, or dreaming sleep. If a person is in REM sleep, the eye balls will move back and forth underneath the eye lid.

REM sleep is very important for learning and memory. Scientists use electroencephalography (EEG) to measure electrical changes in the brain to better understand sleep. During waking hours, the EEG shows small and fast brain waves, called alpha rhythm. In the first stage of sleep known as NREM 1, the EGG shows relatively fast brain waves, called theta rhythm. The second stage of sleep, NREM 2, brain waves are fast and interspersed with big waves called K complexes and sleep spindles. The last stage of sleep, NREM 3, is known as deep sleep. During NREM 3, many of the neurons fire together in symphony and create large, slow delta waves, called beta rhythm. These waves appear to be similar to those present during waking hours. We experience approximately 5 cycles of NREM/REM sleep each night, and it takes us about 90 minutes to go from being awake to the first deep sleep of the night. NREM sleep is typically longer during the first part of the night, while REM sleep lengthens in the early morning. REM sleep is also a period of heightened physiological activity, increased heart rate and dreaming.