National Sleep Foundation

Chapter 5: Circadian Rhythm Sleep Disorders

Etiology/Risk Factors

What are the etiology and the risk factors of shift work disorder?

The ability to tolerate shift work may depend on the direction of shift rotation: a clockwise [day – evening – night] is tolerated better than counter-clockwise rotation  (night – evening – day). In addition, the frequency and regularity of the shift work has an impact, with slow and predictable rotations being better tolerated.
The individual’s circadian rhythm also has an impact; for example, morning type individuals appear to have less tolerance for rotating work, compared to evening types, and would have more tolerance for morning shift work schedules.    

There may also be a genetic component to the disorder.  Night-shift workers carrying the five-repeat variant of the Period 3 gene (PER3–/5) “show significantly elevated levels of sleepiness during night-shift hours on both the MSLT and the ESS. In both cases, PER3–/5 shift workers showed sleepiness in the pathological range, while their PER34/4 counterparts showed sleepiness within normal limits. PER3–/5 night workers also show a mean circadian phase 6 hours earlier (i.e. less adapted) than PER34/4 workers.” 
Persons suffering from a comorbid medical or psychiatric disorder, another sleep disorder, and/or those who are light and tenuous sleepers may be at increased risk of developing Shift Work Disorder.

References

95. Lavie P, Tzischinsky O, Epstein R, Zomer J. “Sleep-wake cycle in shift workers on a "clockwise" and "counter-clockwise" rotation system,” Isr J Med Sci. 1992: 28(8-9):636-44.

96. Lavie P, Tzischinsky O, Epstein R, Zomer J. “Sleep-wake cycle in shift workers on a "clockwise" and "counter-clockwise" rotation system,” Isr J Med Sci. 1992: 28(8-9):636-44.

97.National Sleep Foundation (NSF), Shift Work Disorder: Shift Work and Lark / Night Owl Tendencies, Arlington, VA: NSF, 2014. Available online at: http://sleepfoundation.org/shift-work/content/shiftwork-and-larknight-owl-tendencies

98. Lavie P, Tzischinsky O, Epstein R, Zomer J. “Sleep-wake cycle in shift workers on a "clockwise" and "counter-clockwise" rotation system,” Isr J Med Sci. 1992: 28(8-9):636-44.

 

99. Drake CL, Belcher R, Howard R, Roth  T, Levin AM, and Gumenyuk V, “Length polymorphism in the Period 3 gene is associated with sleepiness and maladaptive circadian phase in night-shift workers,” J Sleep Research 2014; DOI: 10.1111/jsr.12264.