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Daytime Sleepiness Study

Multiple Sleep Latency Test (MSLT)

The Multiple Sleep Latency Test (MSLT) is a nap study. It is the standard tool used to evaluate people who are thought to have narcolepsy to see how quickly they fall asleep in quiet situations during the day.

The study isolates you from outside factors that can affect your ability to fall asleep. These factors can include:

  • Temperature (too hot or too cold)
  • Light
  • Noise
  • Activity
  • Anxiety
  • Tension
  • Depression
  • Caffeine
  • Drugs and medications

The MSLT also measures your level of daytime sleepiness. Excessive sleepiness is when you are sleepy at a time and place when you should be awake and alert. It affects about 5 percent of the general population.

The study is based on the idea that you should fall asleep in a shorter amount of time as your feeling of sleepiness increases. The MSLT charts your brain waves and heartbeat and records your eye and chin movements. The study also measures how quickly and how often you enter the rapid-eye-movement (REM) stage of sleep.

Reasons for Receiving an MSLT

  • To see if you have narcolepsy. The MSLT counts sleep-onset REM periods (SOREMPS). This is when you enter REM sleep very soon after you fall asleep. REM sleep is normally the fourth and last stage of each sleep cycle and usually begins about 90 minutes after you fall asleep. People with narcolepsy often have two or more SOREMPS in the nap trials.
  • To see if you have idiopathic hypersomnia. Patients with idiopathic hypersomnia fall asleep easily but do not have SOREMPS.
  • To reveal how long it takes you to fall asleep. Normal sleepers tend to fall asleep in approximately 10 minutes or more during the five naps of the MSLT. Due to the wide range of normal times, the results from these nap trials alone are not enough to diagnose a sleep disorder. Doctors must also consider other data, tests, and medical information.

Call the Centegra Pre-Registration Department at (815) 334-5566 to schedule a MSLT.