Q&A – Should an 8-hour shift schedule rotate forward or backward?
Several studies have provided evidence that forward rotations do, in fact, benefit shiftworkers. A 1992 study by Peretz Lavie of a microelectronic factory, for example, focused on how moving to a forward rotation affected sleep and sleep quality. Workers performed skilled manual work requiring a high level of alertness and attentiveness. A group of 11 workers moved to a weekly forward rotation, while a control group stayed on a backward rotation.
Lavie found that workers favored the forward rotation by a 6-to-1 margin, primarily due to improved sleep after the evening and night shifts. Specifically, forward rotators fell asleep 30 minutes earlier after evening shifts. After night shifts, most were able to fall asleep by 9 a.m., whereas backward rotators often slept at random times during the day. In addition, workers on the forward rotation reported moderately higher levels of subjective alertness during day and evening shifts.
“From a biological rhythms point of view, the clockwise rotation permits a quicker adaptation, particularly of sleep times,” Lavie concluded in the Israel Journal of Medical Science (1992; Vol. 28, pages 636-644).
In a 1993 study, Jane Barton surveyed 261 British shiftworkers in a range of industries, including workers at power and steel plants, police officers, air traffic controllers and postal workers.
Overall, Barton found that backward rotators experienced “poorer physical and psychological health, more sleep disruption, more social and domestic disruption, and lower job satisfaction” than forward rotators. She said her results, reported in Ergonomics (1993; Vol. 36, Nos. 1-3, pages 59-64), “add some support for the use of delaying as opposed to advancing systems.”
Why do people fare better on a forward-rotating schedule? A large body of research has shown that the natural sleep-wake rhythm of the human body, when unconstrained by day and night cues, drifts later each day. Therefore on a counterclockwise rotation, going from nights to evenings to days, the body fights its own innate circadian tendencies to drift later each day, making the adjustment to the night shift excessively difficult and often resulting in reduced alertness and chronic fatigue.
Despite the potential health benefits of a forward rotation, shiftworkers may still prefer a backward rotation for social reasons. This is because the weekend break is eight hours longer on a backward rotation than on a forward rotation, and many workers want to maximize the length of their longest break — even if it means shorter breaks between the other shift changes.
In many cases where backward rotations are preferred, workers might not be aware of the potential sleep benefits of changing to a forward rotating schedule. By educating employees and managers on the pros and cons of both schedules, they can make an informed decision on which schedule they would prefer to work.
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