Behavioural microsleeps in normally-rested people

Sleep-deprived people, or those performing extended monotonous tasks, frequently have brief episodes when performance is suspended and they appear to fall asleep momentarily - behavioural microsleeps (BMs). As BM rates are highly variable between normally-rested people, this study aimed to determine whether there is a relationship between propensity for BMs and measures of sleep. Subjects undertook a continuous 50-min 2-D tracking task and BMs were identified with high temporal accuracy based on simultaneous analysis of visuomotor response, tracking speed, tracking error, vertical electrooculogram, and eye-video. BM rates and durations were correlated with measures of sleep (i.e., wrist actigraphy, Epworth Sleepiness Scale, Pittsburgh Sleep Quality Index, and Horne-Ostberg Morning-Eveningness Questionnaire). BMs occurred frequently during the task but rates were highly variable between participants (mean 79.1/h ± 66.2, range 0-226/h). There were correlations between ESS score and BM rate and duration. However, BMs were not related to other sleep measures. Thus, there is a very large variability in BM propensity in normally-rested subjects which cannot be explained by variation in sleep duration, quality, or efficiency. Propensity to fall asleep in situations in which sustained performance is required may be a trait characteristic in normally-rested people.