Effects of irregular versus regular sleep schedules on performance, mood and body temperature

Twelve male college students slept for 38 consecutive nights in the sleep laboratory under strict control of bedtime and wake-up time. Sleep logs, body temperature and performance on an experimenter-paced auditory vigilance and subject-paced addition test were assessed before sleeping in the laboratory, following 38 consecutive nights, and one month afterward to examine the effects of rigidly controlling retiring and awakening times. While large changes in the regularity of sleep occurred during sleep in the laboratory as compared to the normal irregular schedules, no significant changes in EEG sleep stage, performance, or mood were found. Body temperature was found to be higher and, perhaps, more flattened in the initial irregular condition as compared to the regular sleep schedule condition. It was concluded, however, that careful control of sleep and waking times in relatively irregular sleeping college students had little influence on sleep or performance. This finding implies that previous differences reported between groups of regular and irregular sleepers may have been based on personality differences rather than sleep scheduling factors.