Time and Attendance Shifts – Part 2 of 3
August 8, 2012 in Uncategorized
The health consequences of shift work may depend on one’s chronotype, that is, whether one is a day person or a night person, and what shift one is assigned to.
Cognitive effects of shift work
There are four major determinants of cognitive performance and alertness in healthy shift-workers. They are: circadian phase, acute sleep deprivation, chronic sleep deficit, and sleep inertia.
The circadian phase is relatively fixed in humans; attempting to shift it so that an individual is alert during the circadian bathyphase is difficult. Sleep during the day is shorter and less consolidated than night-time sleep.
Acute sleep deprivation occurs during long shifts with no breaks, as well as during night shifts when the worker sleeps in the morning and is awake during the afternoon, prior to the work shift.
Chronic sleep deficit occurs when a worker sleeps for fewer hours than is necessary over multiple days or weeks. The loss of two hours of nightly sleep for a week causes impairment similar to those seen after 24 hours of wakefulness.
The effects of sleep inertia wear off after 2-4 hours of wakefulness, such that most workers who wake up in the morning and go to work suffer some degree of sleep inertia at the beginning of their shift. The relative effects of sleep inertia vs. the other factors are hard to quantify; however, the benefits of napping appear to outweigh the cost associated with sleep inertia.