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Sleep Study

Sleep Study

Alternate Names

  • sleep study
  • rapid eye movement study
  • polysomnogram


A sleep study, or polysomnogram (PSG), continuously measures and records brain and body activities during sleep.

Who is a candidate for the procedure?

A sleep study may be performed if a person has:
  • insomnia or other sleep disorders
  • narcolepsy, which is excessive daytime sleepiness
  • sleep apnea. This condition causes low oxygen levels and frequent wake-ups due either to an abnormality in the brain's mechanism that controls breathing, or, more commonly, to blockage of the upper air passages during sleep.
  • behavior disturbances during sleep, such as sleepwalking
  • lasting nightmares
  • rapid eye movement disorders
  • restless leg syndrome, with abnormal leg movements during the night

How is the procedure performed?

The procedure takes place in a sleep study lab over the course of the night. It is important to try to duplicate normal sleep patterns. Heavy exercise should not be done on the day of the study. A person should also avoid:
  • sleeping pills
  • alcohol
  • stimulant medications, such as diet pills
Usually, the person arrives at the lab around 9 p.m. for the study. A technologist will attach electrodes to the skin and scalp. This may take an hour. The electrodes do not pierce the skin, but are held in place by removable gel and tape.
When the person is ready to go to bed, the electrodes are linked to recording equipment. The technologist sits in a central control area, which is separate from the bedrooms. During the observation period, the person is attached to the following:
  • electocardiogram (ECG), which monitors the heart
  • pulse oximetry, which monitors the blood oxygen level
  • electoencephalogram (EEG), which monitors the brain activity
  • electromyography (EMG), which monitors skeletal muscle activity


"Polysomnography:Overview and Clinical Application", The Merck Manual of Medical Information, Home edition, 1997

Professional Guide to Diseases, Sixth Edition. Springhouse: Springhouse Corporation, 1998.

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