What Is a Multiple Sleep Latency Test (MSLT)?
A multiple sleep latency test (MSLT)
A multiple sleep latency test (MSLT) is a test used to measure daytime sleepiness. For this test, you’ll take at least four to five naps while electrodes measure brain activity. The test determines how quickly falls asleep during the naps, and the pattern of sleep you experience.
An abnormal MSLT may indicate a sleep disorder, including narcolepsy, a condition that causes excessive daytime sleepiness (hypersomnia). MSLT is also used to differentiate between narcolepsy and other conditions that cause sleepiness.
For the test, you’ll be asked to lie down in a comfortable, quiet, dimly lit room and try to take multiple naps, usually every two hours, for a set period — likely four to five times during a full day.
Before beginning the test, you may be asked to:
Stay awake the entire night before the test.
Avoid exercise, caffeine, nicotine, and alcohol the day of the test.
During the test:
Each time you lay down, you’ll be asked to close your eyes and try to go to sleep.
Brain activity will be recorded via sensors (electrodes) attached to your head. You may also have sensors attached to your chest, legs, and chin to monitor your breathing and muscle movements.
During all naps, you may sleep for up to 20 minutes. If you haven’t fallen asleep by that time, the technician will wake you.
MSLT typically lasts for about eight hours, however, it can last longer if you take longer to fall asleep.
A healthy adult generally takes longer than 10 minutes to fall asleep during an MSLT. Most people with sleep disorders fall asleep much more quickly. If you fall asleep quickly during naps — usually less than eight minutes — you may have a sleep disorder.
After the test, the sleep technician will review the recording of brain activity and score them according to standard sleep criteria.
The average amount of time it takes you to fall asleep during the naps is called your sleep latency. Depending on your sleep study results, your doctor will determine if you have a sleep disorder and may recommend other tests to confirm the diagnosis.