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Sleep Studies


Sleep studies are tests that record what happens to your body during sleep to find out what is causing your sleep problems. A polysomnogram (PSG) study checks your brain activity, eye movement, oxygen blood level, heart rate and rhythm, breathing rate and rhythm, the flow of air through your mouth and nose, the amount of snoring, body muscle movements, and chest and belly movements.

Sleep study results are generally available within 1 to 2 weeks. A sleep medicine specialist, family medicine doctor, internist, or pulmonologist can review your results at a follow-up visit. The sleep lab technician will not be able to review the results of the study with you.


Polysomnogram (PSG) study
Brain activity (electroencephalogram, or EEG):

Sleep time, stages of sleep (NREM and REM), and awake time are normal. No abnormal brain activity (such as a seizure) is noted.

Eye movement (electrooculogram, or EOG):

Slow eye movements are present at the start of sleep and change to rapid eye movements during REM sleep.

Muscle movement (electromyogram, or EMG):

No leg jerking or other abnormal muscle movement is present.

Blood oxygen (O2) level (oximetry):

Blood O2 level (oximetry) is greater than 90%.1

Heart rate and rhythm (EKG, ECG):

Heart rate and rhythm are normal. No heart rate changes (arrhythmias), such as an abnormally slow or fast heart rate, are noted.

Breathing effort (respiratory disturbance index, or RDI):

No reduced air flow (hypopnea) or blocked air flow (apnea) to the lungs is found.

Chest and belly movements:

The chest and belly move normally throughout the study.

Audio and video recordings:

Sleep is restful and not disturbed. Night terrors, sleepwalking, and sleep talking do not occur.

Snoring monitor:

Excessive snoring or abnormal snoring patterns are not present.

Airflow monitors:

Airflow through the mouth and nose is not blocked.

Multiple sleep latency test (MSLT)
Sleep onset:

Taking 10 to 20 minutes to fall asleep is normal.

Maintenance of wakefulness test (MWT)
Sleep onset:

Being awake for about 40 minutes is normal.

Abnormal values

  • For a polysomnogram, reduced or blocked air flow to the lungs (RDI value) that occurs more than 5 times in 1 hour may mean you have sleep apnea.
  • For a multiple sleep latency test (MSLT), taking an average of 5 to 10 minutes to fall asleep means you have mild to moderate daytime sleepiness. An average of less than 5 minutes to fall asleep means you have severe daytime sleepiness. An average of less than 8 minutes to fall sleep along with 2 or more rapid eye movements (REM) during 5 to 6 naps means you may have narcolepsy.
  • For a maintenance of wakefulness test (MWT), falling asleep in less than 40 minutes is considered abnormal. This means you have severe daytime sleepiness. People who have narcolepsy also may have abnormal test results.

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WebMD Medical Reference from Healthwise

Last Updated: September 09, 2014
This information is not intended to replace the advice of a doctor. Healthwise disclaims any liability for the decisions you make based on this information.

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