Study Examines Role of Metabolism in Night Shift Worker Health

Individual organs in the digestive system contain separate biological clocks that may influence the metabolism of people who work the night shift and help explain a link to shift worker health problems such as obesity and diabetes, a recent study from researchers at Washington State University (WSU) suggests.

For the study, the researchers asked 10 men and four women to simulate a shift work schedule for one week at the WSU sleep lab. Half of the participants fulfilled three days of night shift work, while the other half completed three days of day shift work. After this time, participants remained awake in a semi-reclined posture for 24 hours, receiving the same snacks each hour and giving blood samples every three hours. Room temperature and light exposure were constant.

Researchers analyzed the levels of 132 metabolites, or products of metabolism, during the 24-hour period. Findings showed that 24-hour rhythms in metabolites related to the liver, pancreas and digestive tract shifted by 12 hours after night shift work. However, the brain’s typical 24-hour circadian clock – long regarded as the body’s driving force – shifted by only about two hours, producing conflicting information for the body.

“No one knew that biological clocks in people’s digestive organs are so profoundly and quickly changed by shift work schedules, even though the brain’s master clock barely adapts to such schedules,” Hans Van Dongen, study co-author and WSU professor, said in a July 31 press release. “As a result, some biological signals in shift workers’ bodies are saying it’s day while other signals are saying it’s night, which causes disruption of metabolism.”

Previous research has shown that regular night shift workers face an increased risk of becoming obese or overweight, conditions that are associated with cardiovascular disease, among other adverse health issues.

The study was published online July 10 in the journal Proceedings of the National Academy of Sciences.