Multiple Sleep Latency Test (MSLT)

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Multiple Sleep Latency Test (MSLT)

Do you find it difficult to keep your eyes open during the day, or that you often fall asleep without warning or control? You may be experiencing a sleep disorder, a disruptive medical issue that interferes with your body’s sleep patterns. Sleep disorders can have a wide range of symptoms, but the vast majority of them interfere with your ability to sleep and cause fatigue which can result in severe effects on your physical and mental health.

One of the most effective ways to address a sleep disorder is by undergoing some form of sleep study. A sleep study allows a specialist to analyze your sleep patterns and brain activity during sleep to determine the cause of the problem. There are many different tests that a sleep study may use, one such test being a multiple sleep latency test (MSLT). If you believe you have a sleep disorder, read on to learn more about multiple sleep latency tests, and if it may be the right kind of sleep study for you.

What Is the Multiple Sleep Latency Test?

The MSLT measures how long it takes for a person to fall asleep throughout the day by using a series of scheduled naps. It also determines whether REM sleep occurs upon falling asleep, which is usually an indication of whether or not someone is properly sleeping. If a person is unable to reach REM, or there are other complications with them falling asleep, they likely have a sleep disorder.

What Can an MSLT Diagnose?

While some sleep studies have a wide range of utility that can be used to diagnose multiple sleep disorders, an MSLT is better suited for diagnosing specific indications. The primary sleep conditions that an MSLT is used to diagnose are narcolepsy and idiopathic hypersomnia.

Narcolepsy is characterized by overwhelming daytime sleepiness, and difficulty staying awake for long periods of time, whereas idiopathic hypersomnia is simply marked by excessive daytime exhaustion even after a good night’s rest. These conditions can often be difficult to differentiate between regular feelings of tiredness, but the analysis done by an MSLT allows sleep specialists to better identify a legitimate problem.

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Who Should Receive an MSLT?

If you’re constantly sleepy throughout the day for no apparent reason, or you’re sleepy in situations that require a constant sense of alertness, such as driving, you’re likely a good candidate for an MSLT. Feeling excessively sleepy in these scenarios can be disruptive to your daily life, and potentially harmful if you fall asleep behind the wheel. It’s best to get an MSLT as soon as possible if feelings of extreme sleepiness intrude on your life, so any harm that would come to you as a result can be prevented.

How To Prepare for an MSLT?

There are many factors that can interfere with an MSLT and result in a failed test or inaccurate information. These include anxiety, depression, and the amount of sleep you get prior to the study, so a sleep doctor may recommend that you take certain steps to fully prepare for your MSLT.

The most common preparations are as follows:

  1. Keep a sleep diary for two weeks and try to maintain a regular sleep schedule so your doctor can identify any sleep patterns. This may also allow your doctor to build a theory on what’s causing your daytime sleepiness before the MSLT is conducted. It will also ensure you get the proper amount of sleep to complete the test as instructed.
  2. Discuss any dietary or medical use of stimulants such as caffeine with your sleep doctor prior to the test. If you are on any medications, your doctor will instruct you on when to use your medications before the MSLT. Some medications may have to be stopped entirely for a few weeks before the test. Full cooperation will be required to ensure the MSLT bears the most accurate results possible.
  3. The night before your MSLT, a separate sleep study is conducted to ensure the MSLT goes as planned. For results to be accurate, you will need to sleep for at least six hours during this initial sleep study to determine if a separate disorder such as sleep apnea is causing your excessive daytime sleepiness.
  4. You may be required to take a drug test the morning of the MSLT. This is to ensure that the test will be accurate, and no substances will interfere with the final results. The results of this drug test will be kept private between you and your doctor.

What to Expect During an MSLT

In order to get the most accurate results, an MSLT takes place over most of the day. During the test, you’ll attempt to take five naps at set times with 2-hour breaks in between. If you are unable to fall asleep for one of these naps within a certain amount of time, you will skip that nap and wait until the next one. In some cases, only four naps is enough to complete the study.

As you sleep, you will have sensors on your head, face, and chin to monitor if you’re asleep. These sensors will also detect whether or not you’re in REM sleep, and how quickly you reached this stage. If you have narcolepsy, you’ll fall asleep fast and enter REM sleep faster than most people.

Understanding Your Results

When the MSLT is complete, it can take a few weeks for results to come in. During this time, a sleep specialist will analyze how fast you fell asleep and whether or not you entered REM sleep, and reference it with the time it takes most people to do the same. People with narcolepsy who take an MSLT usually fall asleep in less than 8 minutes on average, and if that is the case for you, it’s likely that you have narcolepsy.

When You Should Contact Your Doctor

If your life is being disrupted by a sleep disorder, it’s important to contact your doctor as soon as possible. Narcolepsy and other sleep disorders can cause significant harm to your health, and addressing them with a sleep study like the MSLT can prevent your condition from worsening.

If you’ve received your results from an MSLT, and they indicate you may have narcolepsy, notify your doctor right away so they may help you pursue additional treatment.

USA Sleep Diagnostic Services provides numerous sleep studies, including the MSLT, so we can help you discover the true nature of your problem. Our team of certified sleep specialists is fully committed to quality care, and we want you to leave one of our sleep centers knowing that you’ll be able to sleep better in the future. To get started with an MSLT, you can reach our team at +1-888-792-4445 or email us at

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For more information on at home sleep studies or to find out more about sleep apnea, call USA Sleep Diagnostic Services today!

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