Working in night shifts increases risk of heart disease, cancer: Study

Scientists, including one of Indian origin, have found that working in night shifts increases risk of developing obesity and diabetes, which may lead to heart diseases, stroke and cancer.

The research, undertaken by scientists from Washington State University (WSU) in the US, dispelled the belief that the day-night cycle of the body is driven by brain's master clock, and revealed that separate biological clocks in the liver, gut and pancreas have a mind of their own.

"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," said Hans Van Dongen from WSU.

"As a result, some biological signals in shift workers' bodies are saying it is day while other signals are saying it is night, which causes disruption of metabolism," he said.

"We believe ours is the first study to suggest a mechanism for the connection between shift work and chronic kidney disease," said Shobhan Gaddameedhi, a professor at WSU.

The research also has implications for the study of other chronic diseases that the shift-workers are prone to including, chronic kidney disease and breast, skin and prostate cancer.

The researchers, however, said that it is first and foremost important to unravel the link between shift-work and mentality.

"It is possible that changes in the metabolism of shift workers are associated with altered activity of cellular processes that may be involved in cancer development later in life," Gaddameedhi said.

"Once we understand those cellular processes, we could potentially identify the genes involved and use that knowledge to find ways to prevent cancer in shift workers," he added.

The study analysed the blood samples for metabolites - products of chemical reactions involved in digestion - from blood samples of 14 healthy volunteers who had just completed either a simulated day shift schedule or a simulated night shift schedule.

They found that, following the night shift schedule, 24-hour rhythms in metabolites related to the digestive system had shifted by a full 12 hours, even though the master biological clock in participants' brains had only moved by about two hours.

"Twenty-seven metabolites followed a 24-hour rhythm during both the simulated night and day shift schedules," said Debra Skene, a professor at the University of Surrey in the UK.

"Of these, 24 displayed a dramatic 12-hour shift in rhythm following the simulated night shift schedule, which was not observed following the day shift schedule. This indicated that just three days of being on a night shift schedule has the potential to disrupt metabolism," she said.

"Pinpointing the disrupted metabolic pathways will help unravel the mechanisms underlying shift work and metabolic disorders," Skene said.