Sleep Studies


What are sleep studies?

Sleep studies are tests that record specific body functions during sleep. Body functions measured during sleep may include heart rate, breathing rate and airflow, brain wave activity, eye movement, blood oxygen level and muscle movement.

Why do I need a sleep study?

Your doctor may suggest a sleep study if they think you have a sleep problem. Sleep studies help diagnose sleep disorders such as sleep apnea, narcolepsy, parasomnias or insomnia. Another reason to conduct a sleep study is to help determine if a particular treatment, such as positive airway pressure (PAP) therapy for patients with breathing problems during sleep, is working properly.

What are the symptoms of sleep disorders?

You might have a sleep disorder if you have any of these common symptoms:

  • Snore loudly during sleep.
  • Wake up suddenly gasping for breath.
  • Feel tired and sleepy during the day.
  • Toss and turn/are restless during sleep.
  • Have difficulty falling asleep and staying asleep.

What types of tests are performed in a sleep study?

An in-lab sleep study — or polysomnogram (PSG) — is a comprehensive test used to diagnosis sleep and wake disorders. These tests are conducted overnight at a sleep study center, hospital or other designated site and are under the direct supervision of a trained sleep technologist.

Common types of in-lab sleep studies are:

  • Diagnostic (routine) overnight PSG: This is a sleep study that looks at the stages of sleep (including the amount of stage 1, stage 2, stage 3, and rapid eye movement (REM) sleep), arousals/awakenings from sleep and body functions during sleep and wakefulness, including breathing patterns, brain wave activity, heart rhythms, and muscle movements. It is usually performed to evaluate sleep-related breathing disorders (sleep apnea) or abnormal movements during sleep (REM sleep behavior disorder or frequent leg movements).
  • Positive Airway Pressure (PAP) titration study: This study is performed after a diagnosis of sleep apnea has been made. The purpose of the study is to determine the appropriate pressure setting of the PAP machine to best treat sleep apnea. The air pressure delivered through the PAP mask is gradually increased while the patient is sleeping until the pauses in breathing that occur with sleep apnea are under control.
  • Split-night PSG with PAP titration. Split night PSG is conducted when severe sleep apnea has been discovered during the first part of the routine PSG. The second half of the night is used to test the settings of the PAP therapy.
  • Multiple sleep latency test (MSLT). This test is a daytime sleep study that consists of five 20 minute nap trials scheduled two hours apart. The test measures a person’s tendency to fall asleep during the normal waking hours. MSLT is used to diagnose narcolepsy or other forms of hypersomnia (excessive sleepiness). To ensure accurate results, it is performed on the morning following a routine overnight PSG.
  • Maintenance of wakefulness test (MWT). This test determines how well you remain awake under situations that make it easy to fall asleep. Patients usually sit in the dark for 40 minutes every two hours during the day, for a total of four trials. This test is used to assess safety risks (for example, the inability to remain awake while driving) and treatments to prevent sleepiness.

What is home sleep apnea testing (HSAT)?

Home sleep apnea testing is a modified type of sleep study that can be done in the comfort of your home. The portable sleep monitoring device records such information as breathing rate and airflow, heart rate, blood oxygen levels and snoring during sleep. This test helps to confirm the suspicion of moderate to severe obstructive sleep apnea.

Home sleep apnea testing is not used as a screening tool for patients without symptoms. It should also not be used in:

  • Patients with significant medical problems (such as heart failure, moderate to severe heart or lung disease or neuromuscular disease).
  • Patients who have other sleep disorders (such as central sleep apnea, restless legs syndrome, insomnia, circadian rhythm disorders, parasomnias, or narcolepsy) in addition to the suspected obstructive sleep apnea.

HSATs are generally mailed out to patients to be used on the night that they are received. Instructions are included to assist patients with how to use the device. Technical support is also available. Packaging and return instructions are included. Results are usually available within one to two weeks after the device has been returned.

Test Details

How do I prepare for my sleep study?

You will receive specific instructions about how to prepare for your sleep study. Some general information is as follows:

  • Do not drink alcohol or consume caffeine-containing beverages and foods (examples: coffee, tea, colas, chocolate, energy drinks, protein bars) for at least eight hours before your study.
  • Tell your doctor about all medications you are taking. You may be asked to temporarily stop taking a medication before your study.

On the day of your study:

  • Keep to your normal meal times.
  • Do not take any naps.
  • Shower and wash your hair but do not apply conditioner, hair spray, gels, or other hair products. Do not apply creams, lotions, powders, perfume, aftershave/cologne, cosmetics or any other products to your face or body. These products can interfere with the recording by electrodes that are placed on your skin.

Typically you do not arrive at your sleep study location until early evening.

What should I bring to my sleep study?

  • Loose-fitting sleepwear for an overnight study; loose, comfortable clothing for a daytime study.
  • Personal toiletry items and a change of clothes for the next day.
  • Book or smartphone while waiting to start the study. Most sleep sites have televisions in the room.

What can I expect during an in-lab sleep study (PSG)?

On the night of your sleep study, you will be assigned to a private bedroom in a sleep laboratory. Near the bedroom will be a central monitoring area, where the technologists monitor sleeping patients.

You will be hooked up to equipment that might look uncomfortable. However, most patients fall asleep with little difficulty.

The equipment used in a sleep test includes:

  • Electrodes. Electrodes on your face, scalp and body send electrical signals to the measuring equipment. These signals, which are generated by your brain and muscle activity, are then recorded. EEG (electroencephalogram) electrodes measure and record brain wave activity. EOG (electro-oculogram) electrodes record eye movements. These movements are important in determining the different sleep stages, particularly rapid eye movement (REM) sleep. EMG (electromyogram) electrodes record muscle activity from the chin area and legs to identify abnormal movements in sleep and help in determining the presence of REM sleep.
  • A nasal-oral airflow sensor records airflow through your nose and mouth.
  • Belts placed around your chest and abdomen measure your breathing.
  • A bandage-like oximeter probe on your finger measures the amount of oxygen in your blood.
  • An ECG (electrocardiogram) records heart rate and rhythm.
  • A snore microphone records snoring activity.
  • A video recorder records body movements, which will be matched against the electrical signals recorded by the electrodes.

Results and Follow-Up

What happens after the sleep study?

The results are reviewed by a sleep study specialist. They will determine if you have a sleep disorder and what type of equipment or treatment you will need. A report will be sent to the provider who ordered the study (usually one to two weeks after the study has been completed). Your provider will communicate the results to you and the next steps.

Last reviewed by a Cleveland Clinic medical professional on 10/29/2019.


  • American Academy of Sleep Medicine. In-Lab Sleep Study. ( Accessed 10/29/2019.
  • National Sleep Foundation. Sleep Studies. ( Accessed 10/29/2019.
  • National Sleep Foundation. Sleep Assessment & Evaluation: Sleep Center/Lab Tools. ( Accessed 10/29/2019.
  • National Heart, Lung, and Blood Institute. Sleep Studies. ( Accessed 10/29/2019.
  • American Thoracic Society. Patient Education/Information Series. Sleep Studies: In the Sleep Laboratory and in the Home. ( Accessed 10/29/2019.
  • Welch KC, Goldberg AN. Chapter 41. Sleep Disorders. In: Lalwani AK. eds. CURRENT Diagnosis & Treatment in Otolaryngology—Head & Neck Surgery, 3e. New York, NY: McGraw-Hill; 2012. Accessed 10/29/2019.

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