The forty-eight hour day

Four normal young adult male subjects were evaluated in a systematically imposed regime of 32 hr of wakefulness and 16 hr of sleep time in an environment free from time cues. Electroencephalographic and electrooculographic recordings were made continuously during the experiment, which lasted for 10 complete cycles. Sleep efficiency was assessed by determining the percentage of sleep time during the assigned sleep period. The average sleep efficiency for the experimental period was 77%. Results, in general, conformed to earlier findings of non-24 hr schedules of sleep and waking: the overall sleep system remains relatively stable across a variety of scheduled variations; however, utilization of the sleep period becomes less efficient as the schedule increasingly deviates from the normal approximately 16 hr wakefulness/8 hr sleep schedule.