Working odd hours increases health risks: study

07 March 2009

Working the night shift might lead to hormonal and metabolic changes that raise risks for obesity, diabetes and heart disease, researchers at Brigham and Women's Hospital and Harvard Medical School in Boston have found.

The researchers, led by Frank Sheer, an instructor of medicine in the division of sleep medicine, have found that night shift work affects much of the human body's biological clock - its circadian rhythm. The internal biological clock keeps day-shift time even when a person goes on the night shift, the team explains.

"In the long run, the physiological impact of shift work on several markers involved in the regulation of body weight - leptin, insulin, cortisol - seems to contribute to the increased risk for the development of diabetes, cardiovascular disease and obesity," said the researchers.

Scheer and his team have reported the findings in the 2 March online issue of the Proceedings of the National Academy of Sciences.

The authors point out that about 8.6 million Americans perform shift work, which the National Sleep Foundation defines as any type of schedule that falls outside the standard nine-to-five norm for business hours. In the United States, factory workers, hospital staff, policemen, firefighters, pilots, road crews and truck drivers are some of the positions that commonly entail some degree of shift work.

This type of work has been previously associated with gastrointestinal problems, fatigue and poor sleep, the researchers noted. Such complications are thought to arise from a chronic disconnect between the waking and eating habits the work demands and the body's innate 24-hour sleep/wake clock, or circadian rhythm.