Description

Shift work disorder (SWD), classified as a circadian rhythm sleep-wake disorder, is characterized by symptoms of insomnia and/or excessive sleepiness when required to work during usual sleep times. SWD is caused by a misalignment between the internal circadian rhythm and the required sleep-wake schedule defined by nontraditional work shifts including night shifts, afternoon or evening shifts, early morning shifts, irregular shifts, and rotating shifts (1).

Epidemiology

Prevalence

• In the United States, ~20% of employed adults are shift workers, particularly in service-related occupations such as health care, protective services, transportation, and food services (1).
• 1 in 3 shift workers is affected by insomnia or some form of sleep disturbance. ~90% of shift workers note daytime sleepiness or fatigue. SWD has an estimated prevalence of approximately 2–5% in the general population of the United States (1).
• Prevalence of SWD rises with age, particularly for adults age >50 years.

Etiology and Pathophysiology

In shift workers, there is a misalignment between one’s endogenous circadian rhythm of sleep and wakefulness and a sleep-wake schedule based on nontraditional shift work. Dyssynchrony results in excessive sleepiness during the work shift and/or insomnia during desired sleep time (1),(2).

Genetics
One possibly genetically linked trait is a person’s preference for the morning versus evening. This is partially linked to the polymorphism of the clock gene PERIOD3 (PER3) involved in sleep-wake regulation (1).

Risk Factors

• Age >50 years (1)
• Strong competing social and domestic needs

General Prevention

• Reduce or eliminate shift work. Try to rotate shifts forward if shifts must be rotated. Use bright light during shifts.
• Improve sleep hygiene. Schedule regular sleep including naps (<1 hour) just before a shift or, if possible, during a shift.

Commonly Associated Conditions

• SWD has been associated with functional consequences including impaired immediate free recall, decreased processing speed, and selective attention impairments.
• SWD has been associated with higher risk of vehicular accidents, job-related injuries.
• SWD has been associated with poor physical health (including increased incidence of gastrointestinal [GI] disorders, cardiovascular disease [CVD], diabetes, and possible increase risk of cancers) as well as poor mental health (including increased incidence of substance use disorders and mood disorders).