(Polysomnogram; Overnight Sleep Study; Rapid Eye Movement Studies)
Michael Jubinville, MPH
Polysomnography (PSG) is a study of sleep cycles and sleep behavior. It is usually done in a sleep center overnight. This study involves observing a person at sleep while charting brain waves and other bodily functions.
Reasons for Test
This study can evaluate sleeping problems such as:
There are no major, lasting problems with this procedure.
What to Expect
Prior to Test
Before the test:
Description of Test
You will arrive in the evening. You will be given time to relax in the room where you will sleep. Electrodes will be attached to your head, legs, and chest. Other monitors are placed around your chest, near your nose and mouth, and on your finger. You will be able to read and relax again until your bedtime.
For most of the night, you will be able to move and turn during sleep. But, you may be asked to try to sleep in a certain position for part of the night. You will be watched by video during the night. This will be done in case sensors come loose. They can also be taken off so you can use the bathroom if you need to. Sometimes, it is clear during the test that you can benefit from an intervention, such as continuous positive airway pressure (CPAP). This may be started midway through the night.
Your doctor may ask for an additional test for narcolepsy. The test is known as the Multiple Sleep Latency Test (MSLT). You will need to stay for part of the next day. You will be asked to nap for up to 20 minutes every 2 hours. The time it takes you to fall asleep and the time it takes you to go into deep sleep will be measured.
Your sensors will be removed in the morning. In most cases, you will be able to go home.
How Long Will It Take?
About 10-12 hours
Will It Hurt?
Results from this test may be ready right away. If not, then they are most often available within 2 weeks. Any abnormal breathing or leg movements during sleep will be noted. Your doctor will review the results and discuss them with you.
Call Your Doctor
There should not be side effects or lasting problems from the study. Call your doctor if you have any concerns.
If you think you have an emergency, call for emergency medical services right away.
American Academy of Sleep Medicine
National Sleep Foundation
Better Sleep Council Canada
Canadian Sleep Society
Polysomnography. EBSCO DynaMed Plus website. Available at: http://www.childre... . Updated April 10, 2017. Accessed August 22, 2018.
Sleep studies. Boston Children’s Hospital website. Available at:
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Accessed August 22, 2018.
Sleep studies. National Heart, Lung, and Blood Institute website. Available at: https://www.nhlbi.nih.gov/health-topics/sleep-studies. Accessed August 22, 2018.
Sleep studies: In the sleep laboratory and in the home. American Thoracic Society website. Available at:
...(Click grey area to select URL)
Updated 2015. Accessed August 22, 2018.
Last reviewed May 2018 by EBSCO Medical Review Board Marcin Chwistek, MD
Last Updated: 8/22/2018
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