On Varying Work-Sleep Schedules: The Biological Rhythm Perspective.
NIOSH 1981 Jul:51-86
Endogenous and exogenous factors influencing the activity sleep cycle were examined by reviewing published studies which considered the rhythm of wakefulness and sleep and the rhythm of deep body temperature. Human circadian rhythms remained in the absence of environmental cues. The majority of studies indicated that rhythms of all variables measured remained synchronized with a common period of approximately 25 hours. Stimuli of various kinds had little effect on human circadian rhythms. Body temperature was most strongly correlated with fraction of sleep. Freerunning, internally desynchronized rhythms were studied from a review of 155 experiments. Fifty five subjects showed internal desynchronization in which overt activity rhythms differed in period from rectal temperature rhythm. Activity sleep cycles with periods of 12 to 65 hours were noted. The rectal temperature period remained approximately 25 hours. Internal phase relationships between several overt rhythms varied from day to day although individual rhythms were constant. Rapid eye movement (REM) sleep propensity decreased with body temperature increases during freerunning internal desynchronization. REM sleep propensity increased when body temperature decreased during rhythms synchronized to 24 hours. The author noted that results supported the hypothesis that sleep structure was dependent on deep body temperature. Rhythm disorders reduced fraction of sleep within total sleep wake cycle in experiments in which subjects had complete control over sleeping time, suggesting that need for sleep was less than normal when the circadian system was in a disintegrated state. Disintegration of the system reduced sleep needs and produced increases in psychomotor performance and subjective well being. The author concludes that rhythm disintegration such as that produced by night work does not necessarily cause loss of well being but represents an additional stressor on the system.
Worker-health; Work-performance; Endocrine-function; Work-intervals; Job-stress; Sleep-deprivation; Worker-motivation; Physiological-response; Psychological-effects; Biological-rhythms;
The Twenty-Four Hour Workday: Proceedings of a Symposium on Variations in Work-Sleep Schedules, Division of Biomedical and Behavioral Science, NIOSH, U.S. Department of Health and Human Services, Cincinnati, Ohio, DHHS (NIOSH) Publication No. 81-127