Many of us are familiar with the symptoms of jet lag: sluggishness, forgetfulness, irritability, maybe an upset stomach. But after a few days, we assume that our bodies return to normal. New research by associate professor Lance Kriegsfeld and graduate student Erin Gibson suggests that perhaps we shouldn’t jump to such conclusions—jet lag may, in fact, have a long-term, deleterious effect on our cognitive abilities.
By essentially flying Syrian hamsters from New York to Paris twice a week for four weeks, Gibson, the lead author of the study, and Kriegsfeld found that even a month after returning to a normal schedule, the animals showed deficits in learning and memory capabilities. Specifically, the hamsters were unable to learn a simple task that a control group could easily master.
The hamsters, of course, weren’t actually strapped onto planes for transatlantic flights. Instead they experienced the equivalent of sunrise six hours earlier than normal, which caused a disruption of the circadian system (the body’s internal 24-hour clock) similar to crossing six time zones. Since it takes one day to recover from each hour of jet lag, the animals were subjected to two “flights” per week to ensure their circadian systems couldn’t readjust.
In the midst of the hamster’s chronic jet lag, Kriegsfeld and Gibson made a startling discovery. They found a 50 percent reduction in new neuron generation in the animals’ hippocampus. In an area of the brain thought to be essential to learning and memory, such a drastic reduction is significant. Jet lag was either preventing new cells from being born or inhibiting cells from reaching maturity. A direct link has yet to be found, however, between the neuron reduction and jet lag’s lingering effects one month after resuming a normal schedule. Nor is it clear if the damage is permanent or if the brain is able to recuperate by rapidly generating more cells to compensate.
Additionally, this new research applies to more than just frequent flyers. Anyone working a job with rotating shifts, including factory workers and medical residents, may encounter issues similar to those of these jet-setting hamsters. “The human body works like an orchestra,” explains Kriegsfeld, and events that tinker with our body’s clocks, like jet lag, essentially “disrupt the body’s conductor. The formerly harmonious systems all working together turn into a cacophony.”