The Multiple Sleep Latency Test

Last updated: April 23, 2019

The information on this website is not intended to replace a one-on-one relationship with a qualified health care professional and is not intended as medical advice. Read our full medical disclaimer.

The Multiple Sleep Latency Test (MSLT) is a diagnostic tool for excessive daytime sleepiness. This is less common compared to a polysomnogram. It works by measuring the time elapsed from the start of a daytime nap period to the first signs of sleepiness. This is sleep latency. The basic premise of this test is that the sleepier the person is, the faster that person will fall asleep. This is a standard tool for the diagnosis of narcolepsy and idiopathic hypersomnia.

This test takes a full day to complete. It consists of five scheduled naps with two-hour intervals. A patient will have to lie quietly in bed and try to go to sleep. The lights in the room will go off. Once this happens, the test will measure how long it will take before the patient falls asleep. The one administering the test will awaken the patient after 15 minutes of sleep. The nap trial will end if the patient fails to fall asleep within 20 minutes of the lights going off.

These nap trials take place in an environment conducive for sleep. The sleep environment is quiet and dark. During a nap trial, the primary consideration is to provide the patient with a sleep environment that is comfortable and without any external factors that may prevent the patient from falling asleep. These factors may include outside noises, interruptions from other people, or bright lights. The clinical technician will use sensors to determine whether the patient is asleep. These sensors will also determine the sleep stage of the patient.

What should a patient do in preparation for the MSLT?

There are some things to consider prior to the MSLT. These include:

  • Keeping a sleep diary. A sleep diary should have at least two weeks’ worth of data. This is a simple log that will help the doctor get an initial glimpse of the patient’s sleep-wake patterns. It can also help establish which factors may have an effect on a patient’s daytime sleepiness.
  • Avoid drinking or eating stimulants. These include caffeinated drinks. The patient should also inform his doctor if he is taking medications. Some medications can affect the results of the MSLT.
  • An overnight sleep study often precedes MSLT. The patient needs to sleep at least 6 hours during the overnight sleep study. An overnight sleep study will help eliminate other sleep disorders which may be causing the excessive daytime sleepiness.
  • The doctor may also require a patient to take a drug test on the morning of the MSLT. A drug test may make the MSLT more accurate.

What happens after the MSLT?

It usually takes about two weeks before a patient gets the results of the MSLT. This will allow the member of the sleep team to carefully examine the results of the MSLT. They will look at the patient’s sleep stages and determine if the patient entered REM sleep.

A sleep medicine specialist will then interpret the test results. The test results will allow the doctor to make a diagnosis. The doctor will then formulate a treatment plan and discuss it with the patient. If another doctor ordered the MSLT, the one who interpreted the results will send it to the requesting physician.

The information on this website is not intended to replace a one-on-one relationship with a qualified health care professional and is not intended as medical advice. Read our full medical disclaimer.

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