Working a night shift can quickly change the schedule of your internal clock, but maybe not the one you'd expect: A newly released Washington State University study shows that rhythms of internal clocks in digestive organs shifted their schedules by 12 hours after just three days of simulated night shift work, while the biological clock in the brain only shifted by 2 hours.
The research shows that changes in metabolism among shift workers, who are more at risk of becoming obese and getting diabetes, along with many other health problems, may have less to do with changes in that master circadian clock than previously thought.
"We always thought the brain clock was sort of the master clock that told all the other clocks what time it is," says Hans Van Dongen, co-senior study author, director of the WSU Sleep and Performance Research Center and a professor in the Elson S. Floyd College of Medicine. "Now we've seen this really shocking result that 'Wow, these body clocks outside of the brain adapt so fast.' That means you have these conflicting signals in the body."
For the study, participants in the WSU sleep lab worked either a simulated day shift for three days, or a simulated night shift, then spent 24 hours awake in the same conditions while researchers drew blood every few hours to be tested for certain metabolites. The work was similar to desk work, even though that's different from the physical labor night workers may be more likely to do, Van Dongen says, because the study needed to control as many variables as possible.
More research is needed to show why the metabolic rhythms adjusted the way they did: It could be related to the sleep schedule, eating schedule, or the level of physical activity, he says.
"That question becomes important when you start asking what can you do about it," Van Dongen says.