Jet Lag Makes Hamsters Dumb

A new study highlights the perils of shifting time zones.

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By Laura Sanders, Science News

SAN DIEGO—In addition to making you groggy and dazed, jet lag may make you stupid. A study presented November 15 at the annual Society for Neuroscience meeting finds that hamsters suffering extreme, chronic jet lag had about half the normal rate of new neuron birth in a part of the brain. What’s more, these animals showed deficits in learning and memory.

Jet lag poses a serious health threat, said study coauthor Erin Gibson of the University of California, Berkeley. Studies have shown that people with work schedules that require them to frequently change their sleep patterns have higher rates of cardiovascular diseases, diabetes and cancer.

Gibson and colleagues subjected hamsters to jet lag by advancing their day and night schedule by six hours every three days for nearly a month. “It would be like a flight from New York to Paris every three days,” Gibson said. The hamsters’ total sleep amount didn’t change, but the hours spent awake and asleep were completely unrelated to the external environment, like an East Coast businesswoman popping out of bed at 3 a.m. in California.

Jet lag decreases the numbers of new neurons being born in the hippocampus by about 50 percent, the team found. Mental function suffered, too: The jet-lagged hamsters were worse at learning which of two chambers contained a desirable running wheel. Even after 28 days of a back-to-normal schedule, the formerly jet-lagged hamsters still showed learning and memory problems. The mismatch between the internal body clock and the external environment “is having a long-term effect on learning and memory,” Gibson said.

It’s unclear exactly how these cognitive problems are induced by jet lag. The sleep hormone melatonin, stress and increased cell death are all possible culprits that need to be explored, Gibson said.

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