November 2020 | Reviewed by: Shelley Hershner, MD and Seema Khosla, MD
What is shift work disorder?
Shift work disorder occurs when you have difficulties adjusting to your wake and sleep times due to your work schedule. For example, you may need to work at night when most people sleep. Early morning shifts can be a problem too when you have to try to fall asleep before your body is ready. When you have shift work disorder, there is a conflict between your body’s circadian rhythms and your work schedule. You may have to be at work when your body wants to sleep. Then when you must sleep, your body expects to be awake.
People with shift work disorder may sleep up to four hours less than the average worker. Shift work disorder causes you to have trouble sleeping or be severely tired. The quality of sleep may be poor, and you may wake up feeling unrefreshed. You may feel fatigued or have trouble concentrating. This can hurt your performance at work and can put you at risk for making a costly mistake or getting injured on the job.
Not everyone who does shift work has shift work disorder. Many people have difficulty initially adjusting to a new shift. If after several weeks you continue to have difficulty falling asleep or staying asleep, or if you feel tired even after sleeping 7-8 hours, you may have shift work disorder.
The symptoms of shift work disorder usually last as long as you keep the same shift work schedule. The sleep problems tend to go away once you begin sleeping at a more conventional time again. Some people may have sleep problems even after the shift work schedule ends.
Shift work disorder is a circadian rhythm disorder. Your circadian rhythms are your body’s internal clock that signals when you are supposed to feel sleepy or alert. Your circadian rhythms operate on a roughly 24-hour schedule. Your body uses light (and the absence of light) to determine how much of the sleep-promoting hormone melatonin it produces. In shift work disorder, melatonin production may occur when you need to be awake and alert for your job. Exposure to sunlight may prevent you from producing melatonin when you are supposed to sleep.
There are several variations of shift work schedules that can cause difficulties. This includes:
- Early-morning shifts
- Night shifts
- Overnight shifts
- Rotating shifts
Some people have a more difficult time with certain shift work schedules. Night owls may adjust more easily to working an evening shift than morning-types. Likewise, morning larks may have an easier time with early morning shifts. Many people have difficulty adjusting to overnight or rotating shifts.