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Circadian Clock Study Shows Why Jet Lag Wipes Us Out

A person looks out the window on an airplane.
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New research has modeled the interactions between our body’s circadian clocks to investigate why jet lag leaves us so fatigued.

Tuning the body’s clocks

A long-distance flight can herald the start of an adventure, a new life or a well-earned break. It will also likely precede a period of drowsiness, fatigue and sleepless nights. Jet lag can ruin a vacation.

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This exhausting condition is caused by a disconnect between our surroundings and our body’s internal circadian clocks. When in our home time zone, our body clocks are set in a careful balance. While it was originally thought that our bodies were set to a single circadian rhythm, research conducted at the turn of the century showed that our body has multiple clocks in tissues throughout the body, set in different rhythms that can each become disrupted by jet lag. These clocks are individually cued. The brain’s internal clock is set by sunlight, whereas clocks in the peripheral organs are set by eating times. The body becomes more vulnerable to disruption as we age.

The new research, published in the journal Chaos, developed a model that maps the links between these clocks and shows how events like jet lag interfere with these careful calibrations.

Yitong Huang, a postdoctoral researcher in the Braun lab at Northwestern University and study co-author, said, “Conflicting signals, such as warm weather during a short photoperiod or nighttime eating — eating when your brain is about to rest — can confuse internal clocks and cause desynchrony.”

“Most studies primarily focus on one particular time cue or a single clock,” Huang added. “Important gaps remain in our understanding of the synchronization of multiple clocks under conflicting time cues.”

To address this gap, Huang and the team built a model that considered the interplay between different clocks. Within the model, two oscillators are linked together, mimicking circadian clock rhythms.

Better sleep through the stomach

The team was then able to explore how this type of linked system would be altered by various external cues. The data suggested that targeting the circadian clock in the gut might be a handy way to accelerate jet lag recovery. “Having a larger meal in the early morning of the new time zone can help overcome jet lag,” says Huang. “Constantly shifting meal schedules or having a meal at night is discouraged, as it can lead to misalignment between internal clocks.”

The team also noted that effects linked to aging, like weakened signaling between clocks and reduced responsiveness to sunlight, made for a more vulnerable circadian system that was slower to recover from disruption.

The team says their next step is to use their model to investigate the factors that stabilize the circadian system. They hope these findings can help develop preventive techniques to stop jetlag and therapies to keep our circadian clocks on time throughout life.

Reference: Huang Y, Zhang Y and Braun R. A minimal model of peripheral clocks reveals differential circadian re-entrainment in aging. Chaos. 2023. doi: 10.1063/5.0157524

This article is a rework of a press release issued by the American Institute of Physics. Material has been edited for length and content.