For flight attendants and other frequent flyers that experience jet lag on a regular basis, a recent study has linked chronic jet lag to increased health risks. The research, published in the July 20 issue of the scientific journal Current Biology, was conducted on female mice with a predisposition to breast cancer. The mice were raised in a simulated environment with changes made to light and temperature once a week, which had drastic effects on sleep patterns.

Results showed that jet lagged mice developed cancer at a more rapid rate than the control group, which did not have any changes made to their habitat. The affected mice developed tumors eight weeks sooner than control mice, and also experienced significant weight gain despite eating the same amount of food. The impacted group was also found to have slept more in response to an irregular sleep-wake cycle.

Study authors from the National Institute of Public Health in the Netherlands surmise that the health issues were linked to the mice’s circadian rhythm, an internal clock that controls bodily functions in nearly every living organism. The mechanism regulates important functions such as breathing, sleeping and digestion. Scientists monitored changes using biological markers, including melatonin and cortisol hormones and body temperature.

Researcher Harry van Steeg compared what the mice endured to flying back and forth from Amsterdam to Australia once a week in the entirety of a single lifespan.  Since human and mice organ structures are nearly identical, scientists expect the findings would be similar in humans.

Mammalian circadian rhythms take into account environmental feedback, such as light patterns. The body’s organs function in accordance and change their timings when there is a disruption to its schedule. In cases of jet lag, an offset circadian rhythm can cause the brain to take longer to adjust, and thus affect other organs. This imbalance is believed to be the cause for arising health issues.

The study concludes that: “Due to the growing 24/7 economy, shift work will become increasingly part of our society and will, therefore, increasingly affect public health outcomes. Our experimental setup provides a unique tool for exploring underlying mechanisms as well as devising countermeasures.”

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