Jet lag clouds memory for a long time

WASHINGTON - Chronic jet lag affects the brain in ways that bring on memory and learning problems which stay for a month after a flight.

Twice a week for four weeks, researchers subjected female Syrian hamsters to six-hour time shifts - the equivalent of a New York-to-Paris airplane flight.

During the last two weeks of jet lag and a month after recovery from it, the hamsters’ performance on learning and memory tasks was measured, the journal PLoS ONE reports.

As expected, during the jet lag period, the hamsters had trouble learning simple tasks that the hamsters in the control group excelled at, according to a University of California statement.

What surprised the researchers was that these effects persisted for a month after the hamsters returned to a regular day-night schedule.

What’s more, the researchers discovered persistent changes in the brain, specifically within the hippocampus - the part that plays an intricate role in memory processing.

They found that, compared to the hamsters in the control group, the jet-lagged hamsters had only half the number of new neurons (nerve cells) in the hippocampus following the month-long exposure to jet lag.

New neurons are constantly being added to the adult hippocampus and are thought to be important for hippocampal-dependent learning, said Lance Kriegsfeld, associate professor of psychology at the University of California, Berkeley, US.

“This is the first time anyone has done a controlled trial of the effects of jet lag on brain and memory function…we see an impact up to a month afterward,” Kriegsfeld said.

“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 behaviour and function.”

This acute disruption of circadian rhythms can cause general malaise as well as gastrointestinal problems because the body’s hunger cycle is out of sync with meal times, Kriegsfeld said.