Chronic Jet Lag a ‘Killer for Mice’

Tests on mice suggest that chronic jet lag and other behavior involving sharp light-cycle changes, like rotating shift work, could shorten a person’s lifetime, according to a new study.

University of Virginia scientists found that disrupting the circadian rhythms, the 24-hour physiological cycle of humans and many animals, for test mice increased the mortality of especially older mice.

The scientists adjusted the light cycle of the mice, moving it for one group six hours forward and another six hours backwards, mimicking changes that humans go through when they take a transoceanic flight or change from a day shift at work to an overnight shift.

They discovered that, for the elderly mice, of those subjected to the backward-shift regimen, 32 percent died. For those hit with the forward-shift schedule, 53 percent died.

But just 17 percent died in the test period if they had not experienced any light cycle alteration.

The researchers noted that they were not sure what caused the accelerated deaths, but they ruled out chronic stress, as measured by levels of corticosterone.

The deaths “could involve sleep deprivation or immune system disruption,” said a summary of the work.

The study was published in the journal Current Biology.

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