Shift work can increase stress, and that may make you more likely to get sick. Lack of sleep from shift work can increase the chance of car accidents and on-the-job accidents. It also can lead to trouble concentrating at work and poor job performance.

Experts also have found that shift workers have a higher chance of getting some health problems, such as colds and the flu, than people who work days.1

Experts don’t know exactly why this sleep disorder raises the risk of health problems. But they suspect that shift work may cause problems because, if you work at night, your body makes less melatonin than it needs. Melatonin is a hormone that helps control sleeping and waking cycles. It also plays a role in keeping you healthy by making your immune system strong and preventing the growth of tumors.

Light and dark affect how the body makes melatonin. Most melatonin is made at night. During the day, light tells your body to make less melatonin. If you work at night in artificial light, your body may be making less melatonin than it needs.