Shift-work disorder

Bradley V Vaughn MD (Dr. Vaughn of UNC Hospital Chapel Hill and University of North Carolina School of Medicine has no relevant financial relationships to disclose.)
Lynn Kataria MD (Dr. Kataria of the Washington DC Veterans Affairs Medical Center has no relevant financial relationships to disclose.)
Antonio Culebras MD, editor. (Dr. Culebras of SUNY Upstate Medical University has no relevant financial relationships to disclose.)
Originally released November 22, 1993; last updated October 1, 2016; expires October 1, 2019

Overview

Over one fifth of workers work on night or rotating shifts. This occupational accommodation is not always well tolerated and may result in shift-work sleep disorder. The authors explain the pathophysiology and treatment of this common circadian rhythm disorder and discuss the implications of the voluntary desynchronization of the natural world to the artificial occupational world. Individuals who go through this voluntary dissociation of their sleep-wake cycle from other circadian rhythms may suffer sleep disturbance and insufficient sleep accompanied by sleepiness during working hours. These individuals also incur greater health risk and increased risk of accidents. The review enables basic understanding of the circadian clock biology and its interactions with the sleep-wake cycle with the aim toward strategic planning of shift work based on circadian principles, thus, reducing morbidity and increasing shift-work tolerance.

Key points

 

• The circadian rhythm evolved as a mechanism to promote alertness during the day and sleep at night.

 

• The circadian adaptation to night shift work is only partial, at best, due to other time clues giving opposing signals to shift the circadian rhythms to the usual time cues.

 

• Night shift work is associated with sleepiness during work hours and poor sleep during off-work hours.

 

• Shift work tolerance varies for each individual and may be age-dependent.

 

• Night shift work may be associated with increased risk of cardiovascular disease and cancer.

 

• Careful planning and appropriate use of time clues may offset some health effects of night shift work.

Historical note and terminology

Shift work is not a new phenomenon. The history of shift work can be traced back to early nomadic tribes that required camp guards and shepherds to be awake and vigilant during normal sleeping hours. The ancient Greeks and Romans used candles and flaming torches to provide light at night, and perhaps a few occupations in these ancient eras required people to stay awake during the night. Soldiers guarded military camps to ensure protection against surprise attacks by enemies. Sailors worked a night watch to make sure the ship did not run aground. As civilizations progressed and artificial lighting became more prominent, communication and transportation of goods during the night expanded, resulting in “24/7” societies.

The 19th century Industrial Revolution, followed by urbanization, demanded the expansion of shift work. Gas and electric lamps made shift work more attainable, and large factories took advantage of the economics of continuous processing to make production more profitable. In the 20th century, social pressures forced companies to reduce the work shift to an 8- to 12-hour day, resulting in an influx of more workers on the job, and more workers exposed to shift work. Additionally, the globalization of many companies and industries demanded the ability for 24/7 communication and availability of goods, resulting in the further growth of shift work.

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