Working just three night shifts throws your body into chaos - study

Even a few days working the night shift can throw off rhythms in your body that regulate blood sugar, energy metabolism, and inflammation. 

Researchers from Washington State University’s findings help shed more light on the link between working irregular schedules and susceptibility to diabetes, obesity, and other metabolic conditions.

“There are processes tied to the master biological clock in our brain that are saying that day is day and night is night and other processes that follow rhythms set elsewhere in the body that say night is day and day is night,” says senior study author Hans Van Dongen, a professor in the WSU Elson S Floyd College of Medicine, in a media release. “When internal rhythms are conflicted and dysregulated, you have this enduring stress in your system that we believe has long-term health consequences.”

Van Dongen adds that the study shows these disrupted rhythms can be observed in just three days, which relays that early intervention to prevent diabetes and obesity is possible. Intervention may also be beneficial for lowering the risk of heart disease and stroke, which is usually higher in night shift workers.

The study authors conducted a controlled laboratory experiment with volunteers on simulated night or day shift schedules for three days. After their last shift, participants were kept awake for 24 hours under constant lighting, temperature, posture, and food intake to measure their internal biological rhythms without external influences getting in the way. 

Blood samples were drawn at regular intervals throughout the 24 hours and analysed to identify proteins in blood-based immune cells.

Some proteins had rhythms closely linked to the master biological clock, which keeps the body on a 24-hour rhythmic schedule. The master clock can withstand varying shift schedules, so these specific protein rhythms didn’t change much on the night shift. However, most other proteins changed their rhythm significantly among the night shift volunteers compared to the day shift workers.

Specifically, the researchers observed that the proteins involved in glucose regulation underwent a nearly complete reversal of glucose rhythms in nightshift participants. They also found the processes involved in insulin production and sensitivity, which generally work together to keep blood sugar levels in check, were no longer working in tandem in night shift participants. 

The researchers believe this could be due to the regulation of insulin trying to reverse the glucose changes triggered by working the night shift. Working at night requires the body to use up and process more glucose. They said this could be a healthy response in the short term because low glucose levels while active can damage cells and organs, but cause problems in the long run.

“We showed that we can see a difference in molecular patterns between volunteers with normal schedules and those with schedules that are misaligned with the innate biological clock,” says Jason McDermott, a computational scientist with PNNL’s Biological Sciences Division. “The effects of this misalignment had not yet been characterised at this molecular level and in this controlled manner before.”

The findings are published in the Journal of Proteome Research.