The detection of brief daytime sleep episodes

Introduction: In the present study we evaluated the characteristics of sleep-onset detection (during daytime nap opportunities) as a function of differing sleep lengths among healthy, asymptomatic subjects. Methods: Twenty subjects were randomized into a Latin square design in which each subject received 1, 5, 10, and 20 minutes of sleep during an MSLT Subjects were asked after each nap if they fell asleep. The rate of sleep detection was analyzed as a function of sleep duration, Results: Three subjects detected sleep onset after 1 minute of sleep, 7 subjects after 5 minutes of sleep, 10 subjects after 10 minutes of sleep, and 14 after 20 minutes of sleep (chi(2) = 9.63, p < .05). Conclusions: The present data indicate the importance of sleep duration in an individual's ability to detect the occurrence of sleep. Importantly, only three subjects detected sleep after 1 minute of sleep, emphasizing the dangerous nature of brief sleep episodes in the context of public safety.