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MSLT Sleep Study – What is a Multiple Sleep Latency Test?

If you have been ordered to undergo an MSLT Sleep Study, this is the article for you, as we will cover everything you need to know about this important diagnostic sleep test, including;

  • What it is
  • How it works
  • What it measures
  • The kind of results it yields
  • Who is the ideal subject for this test
  • How to get the best results for this test
  • How to prepare for the test
  • Where is the best place to receive this test

Getting adequate sleep is important. So, if you’re in need of a test to diagnose sleep problems, it’s important to get the right one.

This article will help you figure out if an MSLT Sleep Study is right for you.

What is an MSLT Sleep Study?

An MSLT Sleep Study (a.k.a. Multiple Sleep Latency Test) is a diagnostic sleep study that is used to measure a person’s level of daytime sleepiness. Because of this, an MSLT sleep study is typically used to diagnose sleep conditions characterised by daytime sleepiness, as well as occasional oversleeping, such as narcolepsy and hypersomnia.

The goal of an MSLT Sleep Study is to measure how long it takes for a person to fall asleep, as well as the sleep stages they experience across multiple daytime nap opportunities. That’s why, if you are particularly susceptible to daytime sleepiness, your doctor might recommend you undergo an MSLT Sleep Study.

What is sleep latency?

Sleep latency is a technical term that defines how long it takes for someone to fall asleep. For example, a healthy person takes about 10-20 minutes to fall asleep, whereas a sleep latency of less than 8 minutes suggests increased sleepiness which could indicate sleep deprivation or another sleep disorder.

Sleep latency is important because it provides an objective measurement as to the quality of sleep that somebody has.

Sleep latency is affected by multiple factors, including;

  • Variations in sleeping habits (i.e. staying up later or going to bed earlier than usual)
  • Alcohol consumption
  • Chronic pain
  • Different medications
  • Sleeping in a different place than usual

What is daytime sleepiness?

Daytime sleepiness (a.k.a. Excessive sleepiness or daytime somnolence) is a sleep condition that involves difficulty staying awake or desiring sleep during the day. While it is normal to feel sleepy once in a while, daytime sleepiness is characterised by how regular the feeling of sleepiness occurs (e.g. almost every day for at least three months).

Symptoms of daytime sleepiness include trouble staying alert, feelings of irritation, memory problems, difficulty focusing, etc. Long term daytime sleepiness can result in adverse health effects, from cognitive impairment to physical problems such as diabetes and heart disease.

How does an MSLT Sleep Study work?

An MSLT Sleep Study is typically conducted the day after another sleep test called a polysomnography. Polysomnography is an overnight sleep test in which you sleep while hooked up to various monitoring devices, such as electrodes and sensors. These measure various factors for your sleep, such as airflow, breathing rate, blood oxygen, heart rate, body position, brain waves and eye movements.

A couple of hours after the polysomnography is complete, you undergo the MSLT sleep study, which involves a series of four or five short naps (around 15 minutes in length) with breaks in between. Both the polysomnography and the MSLT sleep study are monitored by a sleep technician.

What results does an MSLT Sleep Study provide?

The results of an MSLT Sleep Study revolve around sleep latency by measuring how long it takes for you to fall asleep over the course of each nap. They also include measurements of brain waves and eye movements in order to track which sleep stages you experience during each nap.

Two of the primary criteria for diagnosing narcolepsy include;

  • An average sleep latency of less than eight minutes over the course of the MSLT naps
  • The occurrence of REM sleep at least twice over the course of the MSLT naps

Alternatively, it is possible to diagnose idiopathic hypersomnia if you show an average sleep latency of less than eight minutes over the course of the MSLT Sleep Study, but you have less than two occurrences of REM sleep.

Who needs an MSLT Sleep Study?

An MSLT Sleep Study is appropriate for those experiencing excessive daytime sleepiness. However, it is important to distinguish between excessive daytime sleepiness and fatigue. Despite being similar, they are two different conditions, and an MSLT Sleep Study does not diagnose fatigue.

The difference between excessive daytime sleepiness and fatigue is that, while both conditions involve a feeling of sleepiness during the day, excessive daytime sleepiness includes difficulty staying awake whereas fatigue doesn’t.

To determine whether the MSLT Sleep Study is right for you, your doctor may evaluate your sleepiness using the Epworth Sleepiness Scale, in which you rate how likely you are to fall asleep in certain situations; such as sitting and reading or riding in a car for an hour. Your score on this questionnaire provides insight as to whether this study is correct for you.

How can I prepare for an MSLT Sleep Study?

It is important that you do the following before you undergo an MSLT Sleep Study;

  • If you are currently taking any medications, discuss with your referring doctor if you need to change them temporarily for the sake of the test
  • Avoid using temporary sleep medication or drinking any alcohol in the 24 hours that precede the examination
  • Bring something you can use to pass the time in between MSLT naps, as you must stay awake
  • Complete any sleep questionnaire forms or sleep diaries that you are provided with prior to the test
  • If you don’t drink coffee regularly, refrain from drinking any beverages that contain caffeine (such as coffee or tea)
  • If you drink caffeinated beverages regularly, it is advised that you gradually reduce your caffeine consumption in the week preceding the test.

Where can I go for an MSLT Sleep Study?

At Manse Medical, we provide both high-quality diagnosis and treatment for sleep disorders, and can therefore conduct tests such as an MSLT Sleep Study. Book your appointment online by selecting your preferred clinic and choosing from the list of available specialists.

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