Effects of a prolonged 3-hour sleep-wake cycle on sleep stages, plasma cortisol, growth hormone and body temperature in man

After 1 week of a normal control (baseline) period, 7 healthy young adult subjects were subjected to a 3-hr sleep-wake schedule, (ultradian) which was adhered to for 10 days. They were allowed eight 1 hr sleep times, equally spaced throughout each 24 hr period. They were then allowed a normal nocturnal 8-hr sleep time for 7 days. During all lights-out sleep periods, poly-graphic definition of sleep stages and waking time was made. On the sixth 24-hr period of the first week (baseline) and on the eighth 24-hr period of the ultradian period, sequential 20-min plasma samples were obtained by means of an indwelling intravenous catheter. Rectal temperature was obtained at regularly spaced frequent intervals. Despite significant sleep deprivation, a circadian pattern of total sleep time persisted throughout the 10-day ultradian condition. The distribution and amount of REM sleep time was most affected with stages 3–4 sleep least affected. The time of maximum sleep was delayed by approximately 6 hr. The...