Physiological tracers of circadian rhythms and a performance awareness index were examined as predictors of cognitive performance during two sleep deprivation conditions common to occupational shiftwork. Study 1: Thirty-three sleep-deprived participants completed a simulated nightshift. Study 2: Thirty-two partially sleep-deprived participants completed a simulated dayshift. A standardized logic test was used to measure cognitive performance. Body temperature and heart rate were measured as chronobiological indices of endogenous circadian rhythms. Performance awareness was calculated as a correlation between actual and perceived performance. These studies demonstrated a parallelism between performance awareness and the circadian rhythm. Chronobiological changes were predictive of performance awareness during the simulated nightshift but not dayshift. Only oral temperature was a significant independent predictor. Oral temperature predicted an individual's awareness of their own performance better than their own subjective awareness. These findings suggest that using circadian rhythms in applied ergonomics may reduce occupational risk due to low performance awareness.
Keywords: Body temperature; Circadian rhythm; Occupational health.
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