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Sleep Disorders (PDQ®)

Patient Version

General Information About Sleep Disorders

Getting enough sleep is needed for both physical and mental health.

Sleep is an important part of physical and mental health. While we sleep, the brain and body do a number of important jobs that help us stay in good health and function at our best.

Getting the sleep we need:

Sleep has two main phases that repeat during the sleeping period.

There are two main phases of sleep and both are needed in order to get "a good night's sleep." The two main phases of sleep are rapid eye movement (REM) and non-rapid eye movement (NREM):

  • REM sleep, also known as "dream sleep," is the phase of sleep in which the brain is active.
  • NREM is the quiet or restful phase of sleep. It has four stages, from light sleep to deep sleep.

The phases of sleep repeat during the night in a cycle of a non-REM phase followed by a REM phase. Each cycle lasts about 90 minutes and is repeated 4 to 6 times during 7 to 8 hours of sleep.

Sleep disorders affect normal sleep patterns.

Normal sleep patterns differ from person to person. The amount of sleep you need to feel rested may be less or more than others need. If sleep is interrupted or does not last long enough, the phases of sleep are not completed and the brain cannot finish all the tasks that help restore the body and mind. There are five major types of sleep disorders that affect normal sleep.

  • Insomnia: Being unable to fall asleep and stay asleep.
  • Sleep apnea: A breathing disorder in which breathing stops for 10 seconds or more during sleep.
  • Hypersomnia: Being unable to stay awake during the day.
  • Circadian rhythm disorders: Problems with the sleep-wake cycle, making you unable to sleep and wake at the right times.
  • Parasomnia: Acting in unusual ways while falling asleep, sleeping, or waking from sleep, such as walking, talking, or eating.

Sleep disorders keep you from having a good night's sleep. This may make it hard for you to stay alert and involved in activities during the day. Sleep disorders can cause problems for cancer patients. You may not be able to remember treatment instructions and may have trouble making decisions. Being well-rested can improve energy and help you cope better with side effects of cancer and treatment.

Sleep problems that go on for a long time may increase the risk of anxiety or depression.

This summary is about sleep disorders in adults who have cancer, with a section on somnolence syndrome in children.

  • Updated: April 16, 2014