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Post-Thanksgiving Travel? Blame Jet Lag for Your Memory Loss

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Jet lag causes memory and learning problems, according to new research, so please excuse any typos or nonsensical sentence constructions in the following article: I am writing it after flying cross-country for Thanksgiving and a day before my return flight.

According to psychologists at the University of California, Berkeley, chronic jet lag results in brain changes that persist long after a traveler returns to her normal day/night schedule. They know this after subjecting female Syrian hamsters to six-hour time shifts — which equates to a New York-to-Paris airplane flight — twice a week for four weeks. Researchers then measured the sleep-deprived hamsters’ performance on learning and memory tasks during the last two weeks of jet lag and a month after recovery. (More on They All Look the Same: How Racism Works Neurologically)

Not surprisingly, the tired hamsters had more difficulty with tasks that the control-group hamsters mastered. What the researchers — who published their findings last week in the online, open-access journal PLoS ONE — did not anticipate was that they would continue to have trouble for a month after returning to their standard 24-hour schedule.

The researchers also noted persistent changes in the hippocampus, the part of the brain that controls memory processing. In comparison with the hamsters in the control group, the jet-lagged hamsters had just half the number of new neurons in their hippocampi  after enduring a month of jet-lag. Adult humans are constantly welcoming new neurons to their hippocampi; memory problems are associated with a decrease in cell maturation in the hippocampus, according to researcher Lance Kriegsfeld, U.C. Berkeley associate professor of psychology. (More on Physical Risk vs. Perceived Risk: Explaining the TSA Backlash)

“This is the first time anyone has done a controlled trial of the effects of jet lag on brain and memory function, and not only do we find that cognitive function is impaired during the jet lag, but we see an impact up to a month afterward,” says Kriegsfeld. “What this says is that, whether you are a flight attendant, medical resident, or rotating shift worker, repeated disruption of circadian rhythms is likely going to have a long-term impact on your cognitive behavior and function.”

Why exactly does changing time zones result in jet lag? Chalk it up to each individual’s circadian rhythm. When we cross time zones rapidly — as happens with air travel — it upsets our internal clock. (East-bound journeyers have the toughest time resynching their clocks, which I can vouch for. After a week on the east coast, I’m still tired at the wrong times and wide awake late at night.)

Jet back and forth once in a while, and jet lag is not much more than a nuisance. But chronic disruption of sleep cycles can lead to memory and learning problems, decreased reaction times, higher incidences of diabetes, heart disease, hypertension and cancer and compromised fertility. The World Health Organization actually considers shift work a carcinogen. (More on Pediatricians Should Start Screening for Postpartum Depression)

For those who have just returned to work today after a long flight, Kriegsfeld recommends allowing one day of recovery for every one hour in time-zone shift. You might also try taking popping melatonin, which helps regulate your internal clock. My editor gave me a package of melatonin-infused beverages to try out on my way home. I forgot the drinks in her office; guess it was the jet lag at work.

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