Jet lag can not only leave travellers feeling cranky, it can also cause memory and learning problems long after the return to a regular schedule, according to a new study.
Psychologists at the University of California, Berkeley, subjected hamsters to six-hour time shifts, the equivalent of a New York-to-Paris airplane flight, twice a week for four weeks. Even a month after the hamsters had returned to a normal schedule, they had trouble learning simple tasks compared to hamsters in a control group.
"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," Lance Kriegsfeld, an associate professor of psychology at UC Berkeley, said in a release.
As well as performing poorly on tests that gauged learning, the jet-lagged hamsters were found to have only half the number of neurons in the hippocampus, an area of the brain responsible for memory processing, compared to hamsters in the control group.
Previous studies have shown that flight attendants and shift workers have learning and memory problems, decreased reaction times, higher incidences of diabetes, hypertension, heart disease, reduced fertility and cancer.
"The evidence is overwhelming that disruptions in circadian timing have a direct impact on human health and disease," prof. Kriegsfeld said in the release. "We've now shown that the effects are long-lasting, not only to brain function, but likely to brain structure."
The study was published this week in the online journal PLoS ONE.
To deal with jet lag problems, prof. Kriegsfeld said people should allow one day of recovery for every one-hour time zone shift.
On the plus side, if you're travelling to see the in-laws over the holidays and forgot to get them a gift, you now have an excuse.