Wakefulness Test

National Institute of Neurological Disorders and Stroke, Bethesda, Maryland, U.S.A. 

The Maintenance of Wakefulness Test (MWT) was developed as an alternative, physiologically based test of sleepiness (1). The test was designed for use with patients whose sleepiness during the day might adversely affect performance or safety. Reasoning on the basis of face validity, a person who has little difficulty with falling asleep inappropriately should be able to stay awake in a quiet, sedentary situation such as during MWT trails. Beyond the procedure s face validity, there are other rationales for the use of the MWT, as discussed below. 

We now examine MWT operating characteristics in detail. The MWT protocol was devised to, and on the face of things seems to, measure the ability to sustain wakefulness. As Bonnet and Arand have shown, motivation and posture are important factors that can reduce the tendency to fall asleep and reciprocally, although not linearly, increase the ability to maintain wakefulness. The ability to stay awake can, of course, also be influenced by factors including, but not limited 

Under some conditions, feelings of sleepiness may be great and protocols that must be run when subjects are extremely sleepy encounter the problem of floor effects. For example, physiological sleepiness may be so great because of a drag effect that sleep latencies are too short to be above statistical noise. In these circumstances, it is difficult to detect subjects with abnormal sleepiness or to detect the effect of any remedial intervention. 

Another potential explanation for differences between the MSLT and the MWT is that the MWT, because of its instructions to remain awake, adds a nonlinear motivational factor that is not present with the MSLT. The MWT often reveals improvement in treated patients who continue to be physiologically sleepy. Thus, the MWT is sometimes considered to be a way of extending the sensitivity range of the MSLT (13). Reasoning that an MWT is simply an MSLT plus a motivational component (even a nonlinear component) falters, however, because it assumes that motivational factors are not present in the MSLT. Such an assumption with respect to the MSLT is not justified. 

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While correlation may not be the optimal measure of the usefulness of the Epworth scale for discrimination or prediction (32), there also appears to be no categorical association between ESS score and sleep latency (30,33,34). Thus, although the ESS may be predictive of other variables such as general health status (16) or respiratory disturbance index (12), most of the evidence suggests that its association with sleep latency is tenuous. Similar results emerge from studies comparing ESS with the other (newer) objective measure of EDS, the maintenance of wakefulness test (MWT). In a large narcolepsy sample, the correlation between ESS and MWT was weak (r = -0.29, p <. 001) (35). 

Sangal RB, Mitler MM, Sangal JM. Subjective sleepiness ratings (Epworth Sleepiness Scale) do not reflect the same parameter of sleepiness as objective sleepiness (maintenance of wakefulness test) in patients with narcolepsy. Clin Neurophysiol 1999 110 2131-2135. 

Table 1 Maintenance of Wakefulness Test (MWT) Sleep Latency Norms...

Mitler MM, Gujavarty KS, Browman CP. Maintenance of wakefulness test a polysomnographic technique for evaluation treatment efficacy in patients with excessive somnolence. Electroencephalogr Clin Neurophysiol 1982 53 658-661. 

Sangal RB, Thomas L, Mitler MM. Maintenance of wakefulness test and Multiple Sleep Latency Test measurement of different abilities in patients with sleep disorders [see comments]. Chest 1992 101 898-902. 

Doghramji K, Mitler MM, Sangal RB, et al. A normative study of the maintenance of wakefulness test (MWT). Electroencephalogr Clin Neurophysiol 1997 103 554-562. 

Mitler MM, Doghramji K, Shapiro C. The Maintenance of Wakefulness Test normative data by age. J Psychosom Res 2000 49 363-365. 

Subjective (e.g., Epworth Sleepiness Scale) and objective [e.g., Multiple Sleep Latency Test (MSLT)] daytime somnolence quantification does not seem to provide valuable information on patients risks. This could be explained by the fact that sleep-related accidents occur at certain times when behavioral and chronobiological factors play an important role. Medical and legal issues could nevertheless require an objective test, such as the Maintenance of Wakefulness Test (MWT), to confirm that treated apneic patients present a normal level of vigilance. 

Browman CP, Gujavarty KS, Sampson MG (1983) REM sleep episodes during the maintenance of wakefulness tests in patients with sleep apnea syndrome and patients with narcolepsy. Sleep 6 23-28... 

Armodafinil was initially evaluated in healthy volunteers undergoing acute sleep loss using the maintenance of wakefulness test (MWT) and psychomoter vigilance testing (PVT).25 In this single-dose, double-blind, parallel group trial,... 

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