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What Do Sleep Studies Show?

Sleep studies allow doctors to look at sleep patterns and note sleep-related problems that patients don't know about or can't describe during routine office visits. Sleep studies are needed to diagnose certain sleep disorders, such as sleep apnea and narcolepsy.

Your sleep study results might include information about sleep and wake times, sleep stages, abnormal breathing, the amount of oxygen in your blood, and any movement during sleep.

Your doctor will use your sleep study results and your medical history to make a diagnosis and create a treatment plan.

Results From a Polysomnogram

Polysomnogram (PSG) results are used to help diagnose:

  • Sleep-related breathing disorders, such as sleep apnea
  • Sleep-related seizure disorders
  • Sleep-related movement disorders, such as periodic limb movement disorder
  • Sleep disorders that cause extreme daytime tiredness, such as narcolepsy (PSG and MSLT results will be reviewed together)

If you have sleep apnea, your doctor also may use a PSG to find the correct setting for you on a CPAP (continuous positive airway pressure) machine.

A CPAP machine supplies air to your nose and/or mouth through a special mask. Finding the right setting involves adding just enough extra air to create mild pressure that keeps your airway open while you sleep.

Your doctor may recommend a followup PSG to:

  • Adjust your CPAP settings after weight loss or weight gain
  • Recheck your sleep if symptoms return despite treatment with CPAP
  • Find out how well surgery has worked to correct a sleep-related breathing disorder

Technicians also use PSGs to record the number of abnormal breathing events that occur with sleep-related breathing disorders, such as sleep apnea. These events include pauses in breathing or dips in the level of oxygen in your blood.

Results From a Multiple Sleep Latency Test

MSLT results are used to help diagnose narcolepsy, idiopathic hypersomnia, and other sleep disorders that cause daytime sleepiness.

For narcolepsy, technicians study how quickly you fall asleep. The MSLT also shows how long it takes you to reach different types and stages of sleep.

Sleep has two basic types: rapid eye movement (REM) and non-REM. Non-REM sleep has three distinct stages. REM sleep and the three stages of non-REM sleep occur in regular cycles throughout the night.

People who fall asleep in less than 5 minutes or quickly reach REM sleep may need treatment for a sleep disorder.

Results From a Maintenance of Wakefulness Test

Maintenance of wakefulness test (MWT) results can show whether your inability to stay awake is a public or personal safety concern. This study also is used to show how well treatment for a sleep disorder is working.

Results From a Home-Based Portable Monitor Test

Home-based portable monitors might be used to help diagnose sleep apnea. Portable monitors also can show how well some treatments for sleep apnea are working.

Sometimes, home-based monitors don't record enough information. If this happens, you might have to take the monitor home again and repeat the test, or your sleep specialist may ask you to have a PSG.

Results From Actigraphy

Actigraphy results give your doctor a better idea about your sleep habits, such as when you sleep or nap and whether the lights are on while you sleep. This test also is used to help diagnose circadian rhythm disorders.

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Updated: March 29, 2012