The purpose of the MSLT is to determine how quickly a person falls asleep and to assess sleep quality. The examination evaluates whether you fall asleep too easily and quickly, and whether you enter REM sleep i.e. dream sleep.
Multiple Sleep Latency Test (MSLT)
The Multiple Sleep Latency Test (MSLT) is used to examine excessive daytime sleepiness and hypersomnia, such as narcolepsy and hypersomnia.
Check the patient instructions you received in advance for specific preparation guidelines. A polysomnography sleep study is always performed before the MSLT to ensure sufficient sleep the night prior.
Sometimes an actigraphy monitoring or a sleep diary is also requested before the MSLT. These help assess your sleep-wake rhythm.
Avoid using temporary sleep medications and alcohol during the 24 hours preceding the examination.
The MSLT records brain electrical activity, eye movements, muscle tone, breathing, and heart rate using sensors attached to the skin.
During the examination, you lie in bed in a dark room and attempt to fall asleep. Each nap opportunity lasts 20 minutes. There are four or five nap trials throughout the day (between 8:00 AM and 5:00 PM), spaced two hours apart. If you fall asleep during a trial, you are allowed to sleep for 15 minutes.A healthy person typically remains awake for more than 8 minutes during each nap trial.
The MSLT does not require follow-up and does not impose any restrictions on normal daily activities.
The physician who referred you for the examination will inform you of the results and discuss further treatment. Contact your care unit if you have not received an appointment or call time.
The MSLT is painless and carries no risks.
Updated 9.10.2025