What a Multiple Sleep Latency Test Can Reveal About Your Sleep Quality (2025)

A multiple sleep latency test (MSLT), also known as a daytime nap opportunity study, is a sleep study that measures excessive daytime sleepiness. The test evaluates how fast you fall asleep in a quiet environment during the day. It also assesses the sleep stages that you experience during daytime naps.

A multiple sleep latency test differs from other sleep studies because it is given during the day rather than at night. This test focuses on naps and explains why people may fall asleep when they should be awake. Other sleep study tests evaluate overnight sleep patterns.

Purpose of Multiple Sleep Latency Test

A multiple sleep latency test aims to evaluate the severity of excessive sleepiness, which can be a symptom of certain sleep disorders. You may be a good candidate for the test if you have daytime sleepiness that interferes with your daily life despite routinely obtaining at least 11 hours of sleep.

A multiple sleep latency test measures the time it takes to fall asleep after bed, known as sleep latency or sleep onset latency. It is based on the assumption that as physiological sleepiness increases, sleep latency decreases, and the sleepier you become, the faster you fall asleep.

A multiple sleep latency test evaluates the sleep latency of four or five daytime naps spaced two hours apart the day following a night of sleep observation.

What Conditions Can It Diagnose?

Narcolepsy

Narcolepsy is a chronic neurological disorder characterized by excessive daytime sleepiness. It occurs when your brain is unable to control normal sleep-wake cycles. Symptoms can include:

• Falling asleep in the middle of activities such as eating, talking, or driving
  
• Sudden muscle weakness or cataplexy (the sudden inability to move)
• Hallucinations called hypnagogic hallucinations before falling asleep
• Sleep paralysis (the inability to move right before going to sleep or immediately upon waking up)
• Inability to perform normal academic, work, and social activities
  

Idiopathic Hypersomnia

This disorder causes hypersomnia (excessive sleepiness) during the day. Unlike narcolepsy, idiopathic hypersomnia does not involve cataplexy or sudden sleep attacks. Instead, idiopathic hypersomnia has the following symptoms:

• Sleep drunkenness (feelings of confusion or disorientation upon awakening from sleep)
• Daytime naps that do not relieve drowsiness
• Idiopathic symptoms (lack of an identifiable cause)

What to Expect During The Test

A multiple sleep latency test is a full-day sleep test. It is usually performed the day after apolysomnogramorovernight sleep study at a hospital sleep laboratory or outpatient sleep clinic.

The nighttime polysomnogram is necessary to rule out factors that could impact daytime sleepiness. The MSLT may proceed if:

• The nighttime polysomnogram did not indicate untreated sleep disorders.
• The previous night included at least six hours of sleep
• Sleep architecture (the pattern of rapid eye movement (REM) and non-REM sleep) was normal.

Most of the sensors worn during your nighttime sleep study remain in place for the daytime study. These painless sensors record your brain waves and eye movements to assess when you fall asleep and the stages of sleep you reach during your naps.

Two hours after the end of your polysomnogram, you will have the chance to take five scheduled nap opportunities. You can expect the following process during each nap:

• You will lie down in a bed in a dark and quiet room.
• When the lights are turned off, the test measures how long it takes you to fall asleep.
• You will have a 20-minute opportunity to fall asleep. If you do not fall asleep, you will need to get up after 20 minutes. If you fall asleep, you will be woken up after 15 minutes.
• You will likely be asked to complete a questionnaire to assess the quality of your sleep after each nap.
• Between naps, you will have a two-hour break when you can walk around, eat, drink beverages that do not contain caffeine, read, or use a laptop.

How to Prepare

Your healthcare provider will give you specific directions on preparing for a multiple sleep latency test based on existing medical conditions and your symptoms. Your instructions may include:

• Attempt to maintain a regular sleep schedule.
• Keep a sleep diary for one to two weeks before your sleep study to document your sleep habits.
• Wear an actigraph for one to two weeks before your sleep study; an actigraph is a device that looks like a wristwatch and senses movement to determine your sleeping patterns.
• Provide a list of all the prescription and natural medications you take.
• Have a urine drug screen performed on the day of the test.

Before the Test

Since the outcome of your multiple sleep latency test can be impacted by factors such as insufficient sleep, medications, activity, and arousal level, you must follow the directions provided on preparing for a multiple sleep latency test to ensure accuracy. These instructions typically advise avoiding the following:

• Medications that can alter the results of a multiple sleep latency test, when advised by your healthcare provider
• Alcohol, caffeine, marijuana, chocolate, and other sedating or alerting substances
• Nicotine
  

During the Test

For the best results from a multiple sleep latency test, bring everything you need for a good night of sleep. This can include:

• Pillow
• Blanket
• Book or similar items, such as a laptop, to keep yourself entertained between naps
• Meals or snacks if the sleep center does not provide them

Scoring and Meaning of Results

A sleep specialist scores the results of your test to measure your sleep latency (how fast you fall asleep) for each nap and the onset of REM sleep. Data from all naps are combined to create a mean (average) score. Your healthcare provider will discuss the results of your multiple latency sleep test.

Normal sleep latency is between 10 and 20 minutes. Abnormal sleep latency is diagnosed according to the following criteria:

• A positive multiple sleep latency test is diagnosed when your multiple sleep latency is below eight minutes in your naps.
• Narcolepsy is diagnosed if you take less than eight minutes to fall asleep and you enter the REM stage of sleep in at least two naps during the MSL test.
• Hypersomnia is diagnosed if you take less than eight minutes to fall asleep and you enter the REM stage of sleep in fewer than two naps.
  

How Accurate Is an MSLT?

The multiple sleep latency test is considered the gold standard for diagnosing daytime sleepiness. It has been shown to be reliable and valid. An MSLT is part of the diagnostic criteria for narcolepsy and idiopathic hypersomnia.

The MSLT is most accurate when you follow your healthcare provider's preparation instructions. While the MSLT is regarded as highly accurate, the following factors can impact your results:

• Age
• Amount of sleep before the study
• Anxiety
• Caffeine
• Depression
• Drugs and medications
• Tension

Treatment After MSLT Results

Your healthcare provider will discuss your MSLT results and treatment options based on the severity of your condition, its impact on your life, and other factors such as medical conditions.

Treatments for narcolepsy and idiopathic hypersomnia include behavior modifications and medications. You may also need treatment for underlying conditions that may add to daytime sleepiness.

Behavior modifications include:

• Avoid medications or substances such as caffeine and alcohol that promote drowsiness or sleepiness.
• Moderate your caffeine consumption, which can worsen insomnia and result in daytime sleepiness.
• Maintain a regular, healthy sleep schedule.
• Schedule one to two naps daily.

Stimulant medications, or wakefulness-promoting substances, to treat daytime sleepiness, such as:

• Provigil (modafinil)
• Nuvigil (armodafinil)
• Ritalin(methylphenidate)
• Pitolisant(histamine 3 receptor antagonist/inverse agonist)

Other medications include:

• Sedatives to improve nighttime sleep
• Antidepressants to control cataplexy
• Depressants such as Xywav (sodium oxybate) to treat daytime sleepiness and cataplexy
  

Summary

Living with daytime sleepiness can be a debilitating and sometimes dangerous problem. A multiple sleep latency test can be the first step in resolving daytime sleepiness problems. While the test is time-consuming, getting a diagnosis can help you find ways to improve your symptoms.

Ask your healthcare provider for details about this test and why you may need it. If an MSLT is advised, it may help you return to a normal daily lifestyle.