Multiple Sleep Latency Test (MSLT)

What is a multiple sleep latency test?

A multiple sleep latency test (MSLT) evaluates how long it takes you to fall asleep (sleep latency) and what sleep stages you experience during naps. A healthcare provider uses this test to measure excessive daytime sleepiness and diagnose underlying sleep disorders.

What does a multiple sleep latency test diagnose?

An MSLT helps diagnose:

• Narcolepsy.
• Hypersomnia.

When is a multiple sleep latency test performed?

An MSLT is done during the daytime. It’s always performed after an overnight sleep study.

Who is a good candidate for MSLT?

A healthcare provider will recommend an MSLT if you have trouble staying awake during the daytime. This symptom can interfere with your ability to complete your daily routine and meet personal and social obligations at work or school. Daytime sleepiness affects you regularly for several months.

To determine if MSLT is right for you, your provider will likely perform an Epworth sleepiness scale questionnaire first. This is an eight-question self-assessment for your provider to learn more about how daytime sleepiness affects your day-to-day activities.

How does a multiple sleep latency test work?

An MSLT evaluates daytime sleepiness by monitoring you during five scheduled naps. There are two-hour breaks between each nap. You’ll wear sensors during each nap so your provider can track your brain activity and eye movements.

Your provider is looking to see how fast you fall asleep and if you enter rapid eye movement (REM) sleep during a nap. If you enter REM sleep during a short nap, it could indicate an underlying sleep disorder like narcolepsy.

How do I prepare for a multiple sleep latency test?

Your healthcare provider will give you specific instructions to follow before an MSLT. These instructions may include:

• Follow a regular sleep schedule for several weeks before the test.
• Keep a sleep diary to track when you go to bed and when you wake up each morning for at least two weeks.
• Wear an actigraph device to detect sleep-wake activity.
• Make changes to the medications or supplements you currently take (don’t make changes unless a healthcare provider approves it).

An MSLT usually begins the morning after an overnight sleep study (polysomnography). After you wake up from the sleep study, you’ll have a few hours before the MSLT begins. During this time, your provider may offer additional testing, like a blood or urine test (drug screening), as several drugs can affect both sleep and wake/alertness. You may also be asked to take a feedback survey where you’ll describe how well you slept at the sleep center.

What can I expect during a multiple sleep latency test?

The steps of an MSLT are as follows:

1. You’ll lie down on a bed.
2. A healthcare provider will place sensors on your skin.
3. Your provider will test the sensors to make sure everything works.
4. They’ll turn off the lights and leave the room.
5. You’ll take a nap.
6. Your provider will wake you up from the nap after a scheduled time. Each nap lasts at least 20 minutes. They’ll remove the sensors from your skin.
7. You’ll answer a questionnaire about how you feel after your nap.
8. You’ll take a two-hour break. During this break, the time is yours. You’ll need to stay awake during this time. You can leave the sleep center, eat and drink (but avoid caffeine).

You’ll repeat the above steps after each two-hour break. You’ll take up to five scheduled naps during the day.

If you have any questions during your nap period, your provider is right outside of the room. There’s a two-way microphone near the bed so you can talk to your provider if necessary.

Sleep rooms will be dark and quiet. You should wear comfortable clothing during the test.

What if I can’t fall asleep during an MSLT?

It isn’t easy to fall asleep in a new environment, especially when you’re hooked up to sensors that monitor how you sleep. During an MSLT, if you don’t fall asleep after 20 minutes during a scheduled nap time, you’ll enter your two-hour break period before trying again. Your provider will record that it took you 20 minutes to fall asleep, even if you didn’t nap during your napping opportunity.

Certain aspects of the MSLT may prevent you from falling asleep during a scheduled nap time. That’s OK. Your provider will offer other testing methods if this one isn’t a good fit to diagnose what’s causing daytime sleepiness.

To help you sleep, you can bring things from home to the sleep center, like your favorite:

• Pillow.
• Blanket.
• Book.

It’s very important to follow a consistent sleep schedule weeks before the test. You may need to make changes to the medications you take. Changes can also affect the things you eat and drink, especially if you regularly consume products that contain caffeine, like coffee, sodas or chocolate. Nicotine use is discouraged but if unavoidable, you should stop at least 30 minutes before a nap trial.

What can I expect after a multiple sleep latency test?

After the last scheduled nap of an MSLT, you’re free to go home. Your healthcare provider will schedule a follow-up appointment to review your test results.

What is multiple sleep latency test scoring?

MSLT test results combine the following data to assess daytime sleepiness:

• The amount of time it takes for you to fall asleep (sleep latency).
• Brain waves.
• Eye movements.

Test scoring can vary based on how your provider measures data. Your provider will use averages of MSLT data to make a sleep disorder diagnosis if you meet the following criteria:

• Narcolepsy: It takes fewer than eight minutes for you to fall asleep. You enter the REM stage of sleep during at least two naps.
• Hypersomnia: It takes fewer than eight minutes for you to fall asleep. You enter the REM stage of sleep fewer than two times.

The average time it takes to fall asleep is 11 minutes. Most people enter REM sleep after 90 minutes.

A healthcare provider will interpret data from the MSLT along with data from other tests like:

• A sleep diary that you recorded from the past couple of weeks.
• Wearing an actigraph.
• An overnight sleep study.

When should I know the results of a multiple sleep latency test?

Your provider will schedule a follow-up appointment a few days after the MSLT to go over your test results. This timeframe could vary, especially if you need additional testing before your provider can make a complete diagnosis.

What are the next steps after an MSLT?

If you receive a sleep disorder diagnosis after an MSLT, your provider will meet with you to go over possible treatment plans to reduce daytime sleepiness. You may need to take medications or change your sleep routine to manage symptoms.

It’s possible that the results of the MSLT don’t identify a sleep disorder but you could still experience daytime sleepiness. Additional testing may be necessary to diagnose what’s causing this symptom.

How accurate is MSLT for narcolepsy?

An MSLT is a reliable test to diagnose certain types of narcolepsy. Keep in mind that an MSLT isn’t usually the only test your provider will order to make a diagnosis.

When should I call my healthcare provider?

If daytime sleepiness is interfering with your daytime routine, contact a healthcare provider. They may order an MSLT and/or other tests to make an official diagnosis.