Kazunori Araki

Nineteen-hour variation of postural sway, alertness and rectal temperature during sleep deprivation.

Nineteen‐hour variation of postural sway, alertness and rectal temperature during sleep deprivation were studied. Alertness decreased gradually at night and remained low until morning. Postural sway in the eyes‐closed condition increased during early morning. In six of the eight subjects the greatest sway was observed during the 3‐h period when rectal temperature was at its minimum. It is suggested that unbearable sleepiness during sleep deprivation will give rise to measurable impairment of postural balance especially during the time zone of temperature nadir.

Temporal order of sleepiness, performance and physiological indices during 19-h sleep deprivation

Nineteen‐hour variation of subjective sleepiness, performance and physiological indices were assessed during sleep deprivation. Longitudinal data of each index had its characteristic curve through which the values changed from day level to night level. A comparison of the time when each curve crossed its mid‐range (50% value of its range) showed that those of subjective sleepiness and heart rate were significantly earlier than those of tracking error and coefficient of variation of R‐R interval (CVR‐R), P < 0.01. That of rectal temperature was located at between 1:00 and 4:00 am. These temporal relationships were reproducible under two lighting conditions. These results will be useful in considering the occurrence of human errors by night‐time workers in the early morning.