Sleepiness is well established as a cause of road crashes in registered data through crash studies [1-3]. Long term video recordings in field trials also confirm this [4,5], Sleepiness may be an even stronger cause of road crashes than alcohol, and the two interact in a dramatic way [6]. From a preventive and legal point of view, the individual's awareness of this state is a very important question. The paper of Herrmann et al. [7] in this issue of Sleep Medicine demonstrates that this awareness may be surprisingly low. However, the paper raises several important issues that need discussion. The paper describes an experiment using the Maintenance of Wakefulness Test (MWT) as a setting in which participants pressed a button to signal the perception of "signs of sleepiness." This signal was compared to the occurrence of the first "fragment of sleep" (FSF). The latter was defined as a "sleep EEG" (presumably theta activity) >3 s, plus closed eyes and lack of movement. More often than not the subjects failed to signal before the FSF. The authors concluded from the frequent inability to predict the FSF that it is possible to fall asleep without prior awareness.
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