Frequent Flyer Beware: Jet Lag Is Bad for the Memory
May 22, 2001 -- With airplane crashes featured so often on the news, it seems like flying gets more dangerous all the time. Now, frequent flyers may have one more thing to worry about: losing brain cells and memory, according to research reported in the June issue of Nature Neuroscience.
As anyone who has traveled across time zones knows, long flights really throw your body clock out of whack. Although it's not too surprising that you're tired, disoriented, and have trouble concentrating once you reach your destination, researcher Kwangwook Cho reports that the effects may be more long-lasting.
Cho, a neuroanatomist at the MRC Centre for Synaptic Plasticity at the University of Bristol in England, studied two groups of young women who had worked as flight attendants for five years. In Cho's experience, women are more likely to suffer from jet lag than are men.
The 10 women in each group were all healthy college graduates in their 20s. Although both groups put in the same amount of total flight time, the groups differed in the amount of time they had to recover between transcontinental flights crossing at least seven time zones.
Using a special brain scan to measure the size of different portions of the brain, Cho found that the group with five days or less to recover had smaller right temporal lobes -- located on the side of the brain -- than the group given two weeks or more to recover between long flights.
"Jet lag recovery period may be a potential way to eliminate the temporal lobe [shrinking] associated with repeated jet lag," Cho writes.
Cho also tested learning and memory in the two groups.
Even though both groups were tested two days after transcontinental flights, when their body clocks had adjusted to their new time zone, the group with shorter recovery times between transcontinental flights did worse.
"This is a very worthwhile contribution to the [topic] of aircrew working schedules, in that links were found between [transcontinental] travel, the [hormonal] system, and [memory] performance," Greg Atkinson, PhD, tells WebMD. Atkinson, who was not involved in the study, specializes in sport and exercise sciences at Liverpool John Moores University in the U.K.
Previous work by Cho and others has shown that long distance flights stimulate the body to produce a stress hormone called cortisol. While the flight attendants taking transatlantic flights less often had normal cortisol levels, those who crossed time zones more frequently had high cortisol levels in their saliva.
Over the long haul, Cho believes that elevated cortisol due to shifting time zones is responsible for both the loss of brain cells and the memory impairment. The higher the elevations in cortisol levels, the smaller the temporal lobe volumes on MRI.