Identifying shift worker chronotype: implications for health.

Shift workers are at risk for developing serious health issues due to short sleep. One cause of short sleep is circadian misalignment: sleep time is not synchronized with the body's natural circadian rhythms. Although circadian rhythms are strongly driven by the light/dark cycle, humans have individualized sleep time preferences (chronotypes) based on genetics, development, and external influences. Evening chronotype individuals fall asleep later than average and have a higher risk for developing various noncommunicable diseases. What is unclear is the association between chronotype, shift work, and risks for acquiring chronic conditions. This review is focused on shift worker chronotype and associations with obesity. Because of the paucity of research, other health issues connected with circadian misalignment were included, allowing for a total of 21 research studies. Evidence from this review supports chronotype and certain health issues are associated with shift work, even after adjusting for short sleep duration. In addition, there is evidence to support future research on how shift worker chronotype matched with shift timing impacts worker health. Through better understanding of this interface, occupational health providers can provide more comprehensive worker education on the risks associated with shift work and sleep disturbances.