Maintenance of Wakefulness Test (MWT)

The Maintenance of Wakefulness Test (MWT) measures a subject’s ability to stay awake in a quiet, non-stimulating situation for a given period of time. The MWT may be used to evaluate the response to therapy for individuals in whom conditions causing daytime sleepiness have been diagnosed, and is also helpful for those persons who must demonstrate the ability to stay awake for safety and/or employment purposes.

The Maintenance of Wakefulness Test (MWT) is used to quantify how alert the patient is during daylight waking hours. Basically it will illustrate if the patient is able to stay awake during a predetermined time period. The purpose of the MWT is to provide an indication of how well the patient can function, while remaining alert, when there are relatively quiet times of inactivity.

The face validity of this test stems from the notion that the volitional ability to stay awake provides insight into an individual’s capacity to remain awake, and to assess for the response to interventions designed to improve daytime wakefulness.

The MWT should be performed at the following times: when the patient is adherent to therapy for any identified sleep disorder; when patients are on their usual sleep/wake schedule; and only when the patient has experienced an adequate quantity and quality of sleep on the night prior to undergoing MWT testing. Although performing routine polysomnography prior to the MWT is not an essential part of the protocol, it should be considered on the basis of clinical circumstances, and may be helpful for assessing factors that may skew daytime test results.  Sleep logs are not required before the patient undergoes the MWT.

The following protocol has been recommended in the most recent AASM practice parameters.   A four-trial, 40-min protocol is recommended, with 2 h between each trial.  Sleep rooms should be dark and quiet during testing.  Though a 7.5-W nightlight may be used as a light source, delivering 0.1 to 0.13 lux, the room should be maximally shielded from external light.  Room temperature should be set to the patient’s comfort level.  The patient should be seated in bed, with the back and head supported by a bolster pillow for comfort.  A light breakfast is recommended at least 1 h before the first nap trial, and a light lunch is recommended immediately after the second (noontime) nap trial.  Smoking should be stopped at least 30 min before test initiation. In addition, stimulating activities should be stopped 15 min before each nap.  The use of caffeine, tobacco, or other medications should be discussed and decided on before the test day.  Exposure to bright sunlight is discouraged on the testing day.

The recommended recording array for MWT is the same as that used for the MSLT, including frontal, central, and occipital EEG derivations, and right and left electrooculogram, ECG, and mental/submental electromyogram leads.  After bio-calibrations, the patient is instructed to “please sit still and remain awake as long as possible.  Look directly ahead of you, and do not look directly at the light.”  Patients are also instructed to avoid extreme behaviors to stay awake, such as singing, slapping the face, or pinching.

Sleep latency, stages of sleep, total sleep time, and mean sleep latency across the four naps are recorded, as are the start and stop times for each nap.  Sleep onset occurs with the first epoch demonstrating at least 15 s of consecutive sleep.  The trial ends after 40 min if no sleep occurs, or after unequivocal sleep, which is designated as three consecutive epochs of non-REM stage N1 sleep or one epoch of any other stage of sleep.

The premise of the Maintenance of Wakefulness Test is based on the concept that our ability to stay awake may prove more important than our ability to quickly fall asleep. This is especially true in cases where a patient, who is diagnosed with a sleep disorder, has started treatment. It can also be used to determine if a patient is too fatigued to drive a vehicle or perform other routine daily tasks.

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