Polysomnography

Polysomnography can be done either at a sleep center or in your home. It monitors your sleep through different sleep stages and cycles.

AT A SLEEP CENTER

At the sleep center:

• You will be asked to arrive about 2 hours before bedtime.
• You will sleep in a bed. Many sleep centers have comfortable bedrooms, similar to a hotel.
• The test is most often done at night so that your normal sleep patterns can be studied. If you are a night shift worker, many centers can perform the test during your normal sleep hours.
• A technician will place electrodes on your chin, scalp, and the outer edge of your eyelids. You will have monitors to record your heart rate and breathing attached to your chest. These will remain in place while you sleep.
• The electrodes record signals while you are awake (with your eyes closed) and during sleep. The test measures the amount of time it takes you to fall asleep and how long it takes you to enter REM sleep (rapid eye movement sleep, when most dreaming occurs).
• A specially-trained technician will observe you while you sleep and note any changes in your breathing or heart rate.
• The test will record the number of times that you either stop breathing or almost stop breathing.
• There are also monitors to record your movements during sleep. Sometimes a video camera records your movements during sleep.

AT HOME

You may be able to do your sleep study in your home instead of at a sleep center if the main concern is for sleep apnea. Doing a home sleep study involves spending one night (sometimes two) wearing a monitoring device while you sleep. You may also need to set up your mobile phone to do the test at home. If you have heart or lung disease, your sleep specialist may want you to do the test at a sleep center instead of at home.

Whether the test is at a sleep study center or at home, you prepare the same way. Unless asked by your sleep specialist, do not take any sleep medicine and do not drink alcohol or caffeinated beverages before the test. They can interfere with your sleep.

The test helps diagnose possible sleep disorders, including obstructive sleep apnea (OSA). Your health care provider may think you have OSA because you have these symptoms:

• Daytime sleepiness (falling asleep during the day)
• Loud snoring
• Periods of holding your breath while you sleep, followed by gasps or snorts
• Restless sleep

Polysomnography can also diagnose other sleep disorders:

• Narcolepsy
• Periodic limb movements disorder (moving your legs often during sleep)
• REM behavior disorder (physically acting out your dreams during sleep)

A sleep study tracks:

• How often you stop breathing for at least 10 seconds (called apnea)
• How often your breathing is partly blocked for 10 seconds (called hypopnea)
• Your efforts to breathe
• Your brain waves and muscle movements during sleep

Most people have short periods during sleep where their breathing stops or is partly blocked. The apnea-hypopnea index (AHI) is the number of apnea or hypopnea episodes that occur per hour measured during a sleep study. AHI results are used to diagnose obstructive or central sleep apnea.

Normal test results show:

• Few or no episodes of stopping breathing. In adults, an AHI of less than 5 per hour is considered normal.
• Normal patterns of brain waves and muscle movements during sleep.
  

In adults, an AHI of 5 per hour or above may mean you have sleep apnea:

• 5 to 14 is mild sleep apnea.
• 15 to 29 is moderate sleep apnea.
• 30 or more is severe sleep apnea.

To make a diagnosis and decide on treatment, your sleep specialist must also look at:

• Other findings from the sleep study
• Your medical history and sleep-related complaints
• Your physical exam

Sleep study; Polysomnogram; Split night polysomnography; PSG; OSA - sleep study; Obstructive sleep apnea - sleep study; Sleep apnea - sleep study; HST - home sleep test

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Kirk V, Baughn J, D'Andrea L, et al. American Academy of Sleep Medicine position paper for the use of a home sleep apnea test for the diagnosis of OSA in children. J Clin Sleep Med. 2017;13(10):1199-1203. PMID: 28877820 pubmed.ncbi.nlm.nih.gov/28877820/.

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Updated by: Andrew Schriber, MD, FCCP, Specialist in Pulmonary, Critical Care, and Sleep Medicine, Virtua Memorial Hospital, Mount Holly, New Jersey. Review provided by VeriMed Healthcare Network. Also reviewed by David C. Dugdale, MD, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.