Shift Work Sleep Disorder Overview

Shift work sleep disorder (SWSD) is a condition caused by disruption of the sleep-wake cycle resulting from an irregular work schedule.

Normally, the sleep-wake cycle or circadian rhythm occurs on a 24-hour basis. People who work outside of normal daytime hours, for example, those who work evening shifts or night shifts, those who regularly work extended hours or overtime, and those who work rotating shifts or swing shifts are at increased risk for shift work disorder and other sleeping disorders.

Shift work sleep disorder is relatively common, especially in industrialized areas of the world. It is estimated that more than 15 million people in the United States work evenings, nights, or rotating schedules.

As long as the change is permanent, most people can adjust to working abnormal hours and following a different sleep-wake cycle. This adjustment, called resynchronization, allows many people to function productively during the night and sleep during the day. However, in some cases, especially in people who work a rotating schedule, circadian rhythm disturbances and shift work sleep disorder can occur.

Sleep problems, including shift work disorder and other circadian rhythm disorders such as delayed sleep phase syndrome (DSPS) and jet lag, can be affected by several factors, including age, overall health, and lifestyle. People who are middle-aged and older are at increased risk for many sleep disorders. Aging can contribute to shift work disorder, even in people who have been working irregular shifts for many years.

Medical conditions that may worsen the effects of shift work change include obstructive sleep apnea (OSA), abnormal hormone levels (e.g., testosterone deficiency), and psychological disorders (e.g., depression, seasonal affective disorder [SAD]). Lifestyle choices and family life also can contribute to symptoms of shift work sleep disorder. It often is difficult for people who work irregular hours to participate in normal family activities, holiday celebrations, and get-togethers and still manage to get enough sleep.

Some people function better with little sleep than others and the ability to stay active during different times of the day also varies from person to person. In general, people who wake up and are most active early in the morning usually have a more difficult time adjusting to shift work changes than people who prefer to stay up late at night.

Publication Review By: the Editorial Staff at

Published: 15 Apr 2009

Last Modified: 26 Feb 2015