Shift work disorder can affect your health, as well as your performance and safety on the job.

Physical Health

Shift work has been linked to certain chronic diseases and illnesses. Long-term night shift work is associated with an increased risk of certain cancers, as well as metabolic problems, heart disease, ulcers, gastrointestinal problems and obesity. Insufficient sleep has been shown to change metabolism and appetite, and studies have shown that shift workers have higher levels of triglycerides than day workers. Added to these biological factors, shift workers sometimes have irregular eating habits and poor diet—both of which could increase their risk of metabolic problems as well.

One of the problems could be that when a person works at night, the light exposure suppresses melatonin (which is normally secreted at night). People who work night shifts or rotating shifts also often don’t sleep enough, and long-term sleep deprivation is known to be bad for health. Shift work also disrupts the body’s circadian rhythms and causes them to become out of sync with the external environment and/or behavioral cycles.

Mental Health

Shift work disorder can increase the risk of mental health problems like depression. This may be because of the disruption of the circadian system (which regulates the release of different chemicals in the body). Shift work can also cause certain social issues that decrease wellbeing and happiness. If you work irregular hours, you might eventually feel “out of step” with the people in your family or social network.

Performance

Your productivity and work performance can suffer for several reasons. Shift workers are less likely to sleep the full amount their bodies’ require, and this can accumulate into a large “sleep debt” over time. If you work at night, you’re also going against your biological clock, which is naturally cueing you to become less alert and encouraging you to sleep during the nighttime hours. Both of these factors can slow down your reaction time, and you may not think as quickly or respond and problem solve as well. Your concentration may be reduced, and it can become harder to focus and stay on task. Studies show slower reaction times and more errors occur during night hours.

Safety

As with some occupations, shift work can be a safety risk. Many shift work jobs involve protecting and caring for others, making quick decisions, driving, flying, or operating machinery, so the issue of shift work and safety is an important one. There are many reasons shift work can be dangerous.

Sleepiness leads to slower reactions and interferes with decision making.

Working at night goes against the natural pattern of the body’s clock, so even if a shift worker sleeps enough, a dip in alertness can come at night.

People often misjudge their own sleepiness, believing that they are alert and capable of making good decisions, when in fact their judgment is impaired.

In some fields, shift workers are new to the job or have less experience than their day shift colleagues.

Supervision is sometimes reduced on night shifts.

There are many studies showing safety risks for shift workers. Research shows higher rates of on-the-job injuries for rotating shift workers in factory settings. One study of nurses showed that those who worked nights or rotating shifts were more likely to report poor sleep quality, nodding off at work at least once a week, drowsy driving to and from work, and reporting any accident, error, or “near miss” error. One large scale study of accidents showed a significantly higher rate occurring when workers start their jobs in the evenings, as well as higher accident rates for shifts longer than nine hours. Overall, accidents are more common at night and increase after successive night shifts.