The effects of sleep inertia on decision-making performance

Sleep inertia, the performance impairment that occurs immediately after awa kening, has not been studied previously in relation to decision-making perf ormance. Twelve subjects were monitored in the sleep laboratory for one nig ht and twice awoken by a fire alarm (slow wave sleep, SWS and REM sleep), D ecision making was measured over 10 3-min trials using the 'Fire Chief comp uter task under conditions of baseline, SWS and REM arousal. The most impor tant finding was that sleep inertia reduces decision-making performance for at least 30 min with the greatest impairments (in terms of both performanc e and subjective ratings) being found within min after abrupt nocturnal awa kening. Decision-making performance was as little as 51% of optimum (i.e, b aseline) during these first few minutes, However, after 30 min, performance may still be as much as 20% below optimum. The initial effects of sleep in ertia during the first 9 min are significantly greater after SWS arousal th an after REM arousal, but this difference is not sustained, Decision-making performance after REM arousal showed more variability than after SWS arous al. Subjects reported being significantly sleepier and less clear-headed fo llowing both SWS and REM awakenings compared with baseline and this was sus tained 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.