Clock in at 9am for Maximum Sleep and Minimum On-The-Job Fatigue


Timing your work schedule to clock in between 9am and 2pm can have a positive impact on the quantity and quality of the sleep you get and improve on-the-job fatigue, according to new research presented at the 24th annual meeting of the Associated Professional Sleep Societies in San Antonio.

A research team from Washington State University used mathematical modeling to create 24 separate six-day work schedules by varying shift start times by one hour increments. This was used to predict the effects of work start times and the duration of sleep and on-the-job fatigue.

Those who report to work between the hours of 9am and 2pm were most likely to have eight hours of sleep the night before, the maximum estimated amount. The most optimal time to begin work was 9am.

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Reporting to work between the hours of 8pm and midnight created the most problems for both sleep and on-the-job fatigue. Maximum fatigue occurred when work shifts began at 11 pm. The researchers say that in previous studies nighttime work shifts have been found to disrupt natural circadian rhythms and cause workers to be unable to get quality restorative sleep prior to going to work.

Night workers who begin after midnight, however, did receive a better quality of sleep because they were able to sleep right up until their work schedule, not interrupting their evening circadian rhythm and starting work more rested.

Circadian rhythm is the name given to the “internal body clock” that regulates the 24-hours cycle of biological process in animals and plants, particularly the sleep-wake cycle. The clock in humans is located in the hypothalamus of the brain.

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"Our most interesting finding was that shifts beginning between 8 p.m. and midnight yielded consistently poorer predicted performance and less than adequate predicted total sleep per 24 hours," says study author Angela Bowen, a research assistant at the Sleep and Performance Research Center at WSU. "Shifts of equal duration differ in how fatiguing they are depending on the time of day when they are scheduled. The same limitation on the number of duty hours may be either overly restrictive if during the day or too liberal if during the night."

The researchers said that employers may want to consider this information to create work schedules that maximize sleep and alertness to maximize job performance and productivity.


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