The Effects of a 12-Hour Shift in the Wake-Sleep Cycle on Physiological and Biochemical Responses and on Multiple Task Performance
FEDERAL AVIATION ADMINISTRATION WASHINGTON DC OFFICE OF AVIATION MEDICINE
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Fifteen male paid volunteers ages 20 to 28 were studied in three groups of five each. The first 4 days of the experiment they slept nights 2230 to 0600 and worked days. On the fifth night, they slept only 3 hours 2100 to 2400 before starting a 10-day period in which the wake-sleep cycle was altered by 12 hours. According to the subjective fatigue index, the total fatigue for the awake periods was not significantly changed however, the times within days for greatest fatigue were altered and 9 days were required for a complete reversal of the daily pattern. from shortest to longest mean rephasal times, these were heart rate, norepinephrine, epinephrine, potassium, sodium, internal body temperature, and 17-ketogenic steroids. Performance data based on the Civil Aeromedical Institute Multiple Task Performance Battery suggest the following 1 There was evidence of diurnal variation during the preshift period. 2 There were decrements on the day of the shift following the short sleep period. 3 Performance during the first 3 days following the shift was relatively high for most of the day but was relatively poor in the final session of the day. 4 Performance on the fourth through sixth postshift days was average or above average for the experiment with relatively small variations among the five test sessions per day. 5 Performance on the seventh through ninth postshift days was below average for the experiment and showed some evidence of a return to a diurnal cycling pattern with a new peak period of performance that reflected the 12-hour shift in the wake-sleep schedule.
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