The effects of sleep inertia on decision‐making performance

Sleep inertia, the performance impairment that occurs immediately after awakening, has not been studied previously in relation to decision‐making performance. Twelve subjects were monitored in the sleep laboratory for one night and twice awoken by a fire alarm (slow wave sleep, SWS and REM sleep). Decision making was measured over 10 3‐min trials using the ‘Fire Chief’ computer task under conditions of baseline, SWS and REM arousal. The most important finding was that sleep inertia reduces decision‐making performance for at least 30 min with the greatest impairments (in terms of both performance and subjective ratings) being found within 3 min after abrupt nocturnal awakening. Decision‐making performance was as little as 51% of optimum (i.e. baseline) during these first few minutes. However, after 30 min, performance may still be as much as 20% below optimum. The initial effects of sleep inertia during the first 9 min are significantly greater after SWS arousal than after REM arousal, but this difference is not sustained. Decision‐making performance after REM arousal showed more variability than after SWS arousal. Subjects reported being significantly sleepier and less clear‐headed following both SWS and REM awakenings compared with baseline and this was sustained across the full 30 min. In order to generalize this finding to real‐life situations, further research is required on the effects of continuous noise, emotional arousal and physical activity on the severity and duration of sleep inertia.