Everyone's Health

Travelers Beware, time zones can kill

The mouse that soared, then died

There may be a reason you don't see too many jet-setting rodents (the furry, four-legged kind) around. It seems that doing so – that is, throwing their body clocks out of whack by crossing time zones – is bad for their health.

In a study out of the University of Virginia, researchers found that elderly mice exposed to time shifts that reflect the effects of jet lag tended to die earlier.

There's no indication that jet lag has the same effect on humans, but the study does suggest potential concerns. “Most people report it's more difficult to cross time zones as they age,” said Gene Block, a professor of biology who headed the study. “But whether it's really deleterious, we don't know yet. And we don't know if there is cumulative damage, whether those exposures create problems later on in life.”

The fundamental problem is adjusting to skewed patterns of light and dark. In both rodents and humans, light acts to synchronize body clocks and adjust sleeping patterns. Traveling across multiple time zones or doing shift work can disrupt these systems.

While young and middle-aged mice seemed to handle the time shifts just fine, only 47 percent of the elderly mice (whose age was the equivalent of a person between 70 and 90) survived forward time shifts, and just 68 percent survived backward time shifts.

“It appears that eastward adjustments are more difficult, advances are more difficult than delays,” Block says.

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