The maintenance of wakefulness test (MWT) is procedurally similar to the MSLT. The major differences are: (i) the person being tested is told to "attempt to remain awake" at the beginning of each test session, (ii) the individual is seated rather than laying down in bed, (iii) each test session is 40 minutes in duration, and (iv) poly-somnography the night before testing is not required. Thus, the MWT is used to assess an individual's capability to not be overwhelmed by sleepiness. In a sense, this test is gauging the strength of the wakefulness system (34). If the wakefulness system fails, sleepiness becomes manifest. In the MWT there is no other task than remaining awake and concurrent EEG-EOG-EMG monitoring is conducted to verify success or failure (35,36). In some ways the MWT is a simulation of sedentary inactivity in a nonstimulating environment. Like the MSLT, there are four to six sessions, scheduled at two-hour intervals beginning approximately two hours after awakening from the previous night's sleep. Until standardization at 40 minutes recommended by the AASM Standards of Practice Committee, individual test session durations on the MWT varied from 20 to 60 minutes in different studies. The MWT has proven useful as an outcome measure in clinical trials (37) and is recognized for evaluating noncommercial pilot relicensing after sleep apnea treatment (38). Practice guidelines for MWT were developed along with those for the MSLT. MWT testing is indicated for evaluating individuals whose inability to remain alert constitutes a safety hazard. MWT testing is also recommended to determine treatment response in patients with narcolepsy (or idiopathic hypersomnia). The practice parameter emphasizes the critical importance of clinical judgment and stresses the fact that normal MWT values do not guarantee safety. Recommendations are summarized in Table 3.
TABLE 3 Summary of American Academy of Sleep Medicine Standards of Practice Committee Recommendations for Clinical Use of the Maintenance of Wakefulness Test
MWT is indicated for assessing an individual's ability to remain awake when sleepiness constitutes a public or personal safety issue. MWT may be used to assess response to treatment.
On a 40-minute MWT, 59% of normal subjects remain awake the entire time across all four trials. On the 40-minute MWT A sleep latency less than eight minutes is abnormal A sleep latency between 8 and 40 minutes is of unknown significance The mean (± SD) sleep latency is 30.4 (± 11.2) The upper 95% confidence interval is 40 minutes.
Abbreviation: MWT, maintenance of wakefulness test.
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