Multiple Sleep Latency Test (MSLT) 

A board-certified sleep medicine physician may recommend a daytime nap study or Multiple Sleep Latency Test (MSLT) if they suspect you have excessive daytime sleepiness. Excessive daytime sleepiness occurs if you are very tired when you should be alert and awake.

The MSLT tests for excessive daytime sleepiness works by measuring how quickly you fall asleep in a quiet environment during the day. Also known as a daytime nap study, the MSLT is the standard tool used to diagnose narcolepsy and idiopathic hypersomnia.

Maintenance of Wakefulness Test (MWT)

The Maintenance of Wakefulness Test (MWT) is used to measure how alert you are during the day. It shows whether or not you are able to stay awake for a defined period of time. This is an indicator of how well you are able to function and remain alert in quiet times of inactivity.

What happens during the Daytime Nap Study?

The daytime nap study or MSLT is a full-day test that is typically performed on the day following an overnight polysomnogram (PSG / sleep study). During the MSLT, you will have 5 opportunities to nap throughout the day at 2-hour intervals. We will be measuring and recording the electrical activity from your brain, eyes, and chin muscles. The amount of time it takes you to fall asleep during each nap is also measured. The test provides an objective measure of daytime sleepiness.

You will be awakened after 20 minutes. If you do not fall asleep within 20 minutes, that nap trial will end. Should you fall asleep within the allotted time, the nap will be extended an additional 15 minutes. You will then have a 90-min break in between naps. You will need to stay awake during the break. If you fall asleep, it could potentially render the test invalid. You may then be subject to repeat the study another day. You are free to watch TV or you may bring a book or computer tablet to keep you busy. You will not be permitted to leave the facility at all once the procedure begins, and absolutely no stimulants or sedatives are allowed (e.g., caffeinated drinks, alcohol, cigarettes).

You will also have multiple wires attached to you, with the primary focus on your brain activity. You will take your first scheduled nap an hour-and-a-half to three hours after you wake up from the overnight sleep study. We recommend that about an hour before your first nap trial begins you eat a light breakfast. We have a refrigerator at each facility where you may store your food.

To get you ready for the test

A sleep technologist will place sensors on your head, face, and chin. These sensors are connected to a computer. The wires are long enough so that you can move around and turn over in bed. A series of sensors will measure whether you are asleep. The sensors also determine your sleep stage and read when you are asleep and awake, and transmit data used to determine when you are in REM sleep. During your test, a low-light video camera will allow the technologist to observe your MSLT from a nearby room.

The nap process is repeated five times. After your second (noon) trial, you can have a light lunch. You will need to bring your own snacks/lunch. The office has a refrigerator you may use. After your final nap trial, the sensors will be removed. You are free to leave when the final trial is concluded, usually between 4:00-5:00 pm.


  • On the day of the study, make sure that your hair is clean, dry, and free of oils, hair spray, and other products. Please remove any hair extensions or wigs. The scalp must be accessible.
  • You will have sensors with gel, and possibly tape, placed on your head, chin, and around your eyes to record sleep activity. Please read the following instructions carefully. Avoid alcohol, sedatives, stimulants, and caffeinated beverages (coffee, tea, and cola), for 24 hours before the study.
  • We recommend that patients bring snacks and light meals with them. You will not be allowed to leave the facility until the test is completed.
  • Wear comfortable clothing and feel free to bring your favorite pillow or blanket.
  • Bring your regularly scheduled medications and plan to take them as you normally would unless your physician instructs otherwise. Stimulant medications should not be taken on the day of the study.
  • Bring reading materials, laptop, or other activities to occupy free time. (Wi-Fi is available.)
  • If you are under 18 years of age, a parent or guardian is required to stay with you in the Sleep Center for the entire duration of testing. Most rooms have an overstuffed recliner that is very comfortable for sleeping.
  • Notify us if you require special assistance. You may be required to have a caregiver present during testing.
  • For MSLT, please check with your physician regarding changes in medications. Your doctor might advise you not to take any stimulant medication for two weeks prior to the test.
  • For MWT, please check with your physician regarding changes in medications. Your doctor might advise you to continue to take the stimulant medications on the day of the test.

As we have several locations, please be aware and make note of the CSCC sleep center and suite number where your study is scheduled and the entrance instructions. This information will be emailed to you prior to the study.

If you are unable to keep your appointment or if you have an upper respiratory infection causing significant nasal congestion, contact Comprehensive Sleep Care Center at 703-729-3420 at least 3 business days prior to your scheduled appointment to reschedule. As we schedule our technologists in advance for your sleep study and reserve a room, a fee of $150 will be charged for cancellations within 72 hours of your scheduled sleep study appointment. For more information go to

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Phone: 703.729.3420

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