Robert Wood Johnson University Hospital

Sleep Study

Sleep Study


Procedure overview

Photograph of a woman undergoing a sleep study

What is a sleep study?

Sleep is a state of relative unconsciousness and stillness of the voluntary muscles (muscles that are controlled at will). The stages of sleep range from light to deep and each one has specific characteristics that can be measured. A sleep study consists of a number of medical tests performed at the same time during sleep. The tests measure specific sleep characteristics and help to diagnose sleep disorders. A sleep study may also be referred to as a polysomnogram.

The term "polysomnogram" indicates that there are multiple tests in a sleep study. Breaking the word into parts, "poly" means many, while "somno" means sleep and "gram" means recording - many sleep recordings. The basic recordings may include:

Sleep studies generally take place in a sleep lab during a person's normal sleeping hours. The goal is to record brain and body activity that occurs during sleep so that sleep disorders can be diagnosed and treated.

In addition to polysomnograms, multiple sleep latency tests (MSLT) and multiple wake tests (MWT) may be performed. MSLT's measure how long it takes to fall asleep, while MWT's measure whether you can stay awake during specified times.

Doctors trained in sleep medicine evaluate test results to determine a course of action and resolve sleep related issues. A trained sleep technician will be with you in the sleep lab during the testing period.

What can be measured in a sleep study?

Various body activities and indicators may be measured during a sleep study. Measurements may include:

Reasons for the procedure

Various conditions can cause difficulty with sleep. Common reasons for a sleep study include:

Sleep terrors (nightmares during nondream stages of sleep), sleep walking or talking, and rapid eye movement disorders are less common conditions that may also require a sleep study for accurate diagnosis and treatment.

There may be other reasons for your doctor to recommend a sleep study.

Risks of the procedure

There are no known risks for a sleep study other than possible skin irritation due to the attachment of the electrodes to the skin.

Before the procedure

During the procedure

A sleep study is generally performed on an outpatient basis at night. Procedures may vary depending on your condition and your doctor's practices.

Generally, a sleep study (polysomnography) follows this process:

  1. You will be asked to remove any jewelry or other objects that may interfere with the procedure.
  2. You will be asked to change into pajamas or a hospital gown.
  3. Small metal discs, or electrodes, will be positioned on your head and body for EEG, ECG, EOG, and EMG cables.
  4. Pulse oximetry, which measures the oxygen level in the blood vessels, and air flow monitors, which measure breathing, will be applied to the finger and face, respectively.
  5. The temperature of the room may need to be maintained at a certain level, but blankets can be adjusted as needed.
  6. Lights will be turned off and monitoring will begin before you fall asleep.
  7. For multiple sleep latency testing (MSLT), short nap periods will be assigned at intervals.
  8. For multiple wake testing (MWT), you will be asked to try and stay awake for certain periods of time.
  9. When the study has been completed, the electrodes and other devices will be removed.

After the procedure

Generally, no special care is required after a sleep study and results may take several days. However, your doctor may give you additional or alternate instructions after the procedure, depending on your particular situation.

Online resources

The content provided here is for informational purposes only, and was not designed to diagnose or treat a health problem or disease, or replace the professional medical advice you receive from your doctor. Please consult your health care provider with any questions or concerns you may have regarding your condition.

This page contains links to other websites with information about this procedure and related health conditions. We hope you find these sites helpful, but please remember we do not control or endorse the information presented on these websites, nor do these sites endorse the information contained here.

American Academy of Family Physicians

American Academy of Sleep Medicine

American Board of Sleep Medicine

American Lung Association

National Heart, Lung, and Blood Institute (NHLBI)

National Institutes of Health (NIH)

National Library of Medicine

National Sleep Foundation


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