Multiple Sleep Latency Test

The Multiple Sleep Latency Test (MSLT) tests for excessive daytime sleepiness by measuring how quickly you fall asleep in a quiet environment during the day. Also known as a daytime snooze study, the MSLT is the standard tool used to diagnose narcolepsy and idiopathic hypersomnia.

Frequently Asked Questions

The MSLT is a full-day test that consists of five scheduled naps separated by two-hour breaks. During each nap trial, you will lie quietly in bed and try to go to sleep. Once the lights go off, the test will measure how long it takes for you to fall asleep. You will be awakened after sleeping 15 minutes. If you do not fall asleep within 20 minutes, the nap trial will end.

Each nap will be taken in a dark and quiet sleep environment that is intended for your comfort and to isolate any external factors that may affect your ability to fall asleep. A series of sensors will measure whether you are asleep. The sensors also determine your sleep stage.

Excessive daytime sleepiness occurs when you are sleepy when you should be awake and alert. A board-certified sleep medicine physician will recommend an MSLT if he or she suspects you have excessive daytime sleepiness related to narcolepsy or a hypersomnia. The MSLT is offered at AASM-Accredited Sleep Centers. In order to provide the highest level of care for patients, the AASM requires a board certified sleep medicine physician to review the results of the MSLT.

  • Anxiety
  • Tension
  • Depression
  • Age
  • Caffeine
  • Drugs and medications
  • Amount of sleep prior to the study

The MSLT will last most of the day. Over the course of the day, you will take five scheduled naps. Each of these nap trials is separated by a two-hour break. Depending on the results, a shorter four-nap study may also be used. Be prepared to stay for the full five-nap version of the study.

You will take your first scheduled nap an hour-and-a-half to three hours after you wake up from the overnight sleep study. About an hour before your first nap trial, you will eat a light breakfast.

A sleep technologist will gently place sensors on your head, face and chin. These sensors are connected to a computer. Each is long enough so you can move around and turn over in bed. The sensors show when you are asleep and awake, and transmit data used to determine when you are in REM sleep. Once you are connected, the technologist will test the sensors by asking you to move your eyes, clench your teeth and turn your head. A low-light video camera will allow the technologist to observe your MSLT from a nearby room.

The nap trial begins when the lights are turned off. You will lie quietly in bed and try to go to sleep. The MSLT will measure how long it takes you to fall asleep. It will also measure how long it takes for you to reach REM sleep.

The technologist will awaken you after you have slept for 15 minutes. If you are unable to fall asleep, the nap trial will end after 20 minutes. At this time you will have an approximately two-hour break. You will need to stay awake, and you are free to keep busy in whichever way you choose.

This process will repeat four more times. After your second (noon) trial, you will have a light lunch. After your final nap trial, you will test the sensors again and they will be removed. You are free to leave when the final trial is complete.

Sharon Izak Elaine Chat staff