Hopping the Concorde in New York and heading to Paris for lunch may sound glamorous, but making a habit of this kind of trip may take a toll on your brain.

The right temporal lobe, a part of the brain involved in memory, is smaller in airline crew members who cross multiple time zones and have only 5 days of rest before crossing time zones again.

The crew members were compared with workers who crossed multiple time zones but had 14 days of recovery -- generally working flights that did not cross time zones in that time -- before taking another flight around the world.

The findings are based on magnetic resonance imaging (MRI) data from 20 female flight attendants who spent at least 5 years crossing multiple time zones and who logged a similar number of hours in the sky.

What's more, the researchers observed an association between reduced volume of the right temporal lobe and high levels of the stress hormone cortisol in airline crew members.

And when the women in the study were given tests to check their reaction times, the short-recovery crew performed worse, taking an average of 823 milliseconds to respond versus 741 milliseconds for the long-recovery crew.

A previous study by the investigators found that airline workers subjected to repeated jet lag had higher levels of cortisol, as well as impaired memory.

Adjusting to different time zones can disrupt the circadian rhythm -- the internal clock that regulates when we sleep -- causing the groggy feeling known as jet lag.

The findings of the present study suggest that jet lag recovery period may be a potential way to eliminate the temporal lobe atrophy associated with repeated jet lag.

Past studies of people with depression or post-traumatic stress disorder have shown that high levels of cortisol are associated with a reduction in temporal lobe volume, as well as memory impairment.

Nature Neuroscience May 2001;4:567-568