MSLT (sleep latency test)

What is it?

MSLT, or multiple sleep latency test, is a procedure for identifying readiness to sleep or sleepiness. The test measures how quickly a person falls asleep during the daytime in a quiet environment.



MSLT is performed any time that the client is being examined for narcolepsy and idiopathic hypersomnia or excessive sleepiness. MSLT gives an objective picture of the severity of daytime excessive sleepiness that accompanies sleep disorders. Daytime excessive fatigue accompanies many sleep disorders, most often with sleep-related breathing disorders, such as sleep apnoea.



Our sleep centre uses sleep test devices that allow us to perform clinical and scientific research diagnostics: Philips Respironics Alice 6 LdxS diagnostic system.



  • The procedure is performed the day after polysomnography or the sleep test in the sleep centre, normally between the hours of 9.00-18.00.
  • Alcohol or drinks with caffeine are not allowed to be consumed the evening before or on the day of the test.
  • A drug test may be performed on the examinee on the morning after the MSLT. The drug test ensures that the MSLT results are accurate. Several drugs could influence the test results. The drug test results are private and shall remain between the examinee and treating physician.
  • Smokers should abstain from smoking for at least 30 minutes before the beginning of the next recording.


  • The test consists of four or five recordings.
  • During the test, the sensors record electrical activity in the brain, eye movements, and muscle tone.
  • The examinee is asked to lie down in a darkened room and is then given 20 minutes to fall asleep.
  • If the examinee falls asleep, he shall be allowed to sleep for 15 minutes.
  • If the examinee does not fall asleep within 20 minutes, the sleep test shall be terminated.
  • During the procedure, several questionnaires need to be filled in and the centre staff shall issue guidelines about related activities.
  • The examinee shall be offered breakfast, lunch, and snacks in the sleep centre. The examinee is not allowed to exit the test rooms during the procedure.
  • The examinee shall wear comfortable casual clothing during the procedure
Sleep technologists monitor the recording

Additional information:

In case the patient has already been diagnosed with sleep apnoea, he shall be asked to bring his own APAP treatment device and mask, so the patient would feel comfortable at night.

The result of MSLT procedure can be used to assess the treatment outcome of sleep apnoea in case of excess daytime fatigue.


Test results and treatment:

The sleep doctor shall inform you about the sleep test results during your return visit. The sleep centre administrator shall book you an appointment for this purpose. In addition to test results, the doctor shall introduce you to different treatment options during your return visit.


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