The prevention and treatment of jet lag

Travel across multiple time zones is a common feature of modern life. After transmeridian flights, the internal clocks are desynchronized from the external environment and it can take several days to re-adjust to the new external time cues. The time taken is related to the direction of the flight and to the number of time zones crossed as well as to individual variability. The result of this desynchronization between the human circadian system and the new environmental timing is described as "jet lag". Although the term "jet lag" refers to disturbances in a variety of symptoms, jet-lagged travellers mostly complain of loss of sleep and of its consequences (e.g., diurnal sleepiness, depressed mood, decreased efficiency, premature awakening, etc.). The direct reason for sleep disturbances after a multiple time-zone flight is that sleep is very sensitive to changes in its temporal setting. The present report reviews current data concerning the symptoms of jet lag, the approaches proposed for the alleviation of jet lag and the effectiveness of these strategies. (C) 1999 Harcourt Publishers Ltd.