The effect of four-day round trip flights over 10 time zones on the sleep-wakefulness patterns of airline flight attendants.

To study the effect of a four-day-round trip flight on the sleep-wakefulness of airline flight attendants, subjective sleep-wakefulness and autonomic sleep phases were measured. Forty flight attendants (mean age 33 years, range 21-50) kept daily logs on sleepiness, the time when going to bed, and sleep quality. In addition, the autonomic sleep phases of 21 subjects were studied by the static charge sensitive bed (SCSB) method. After the westward flight, the subjects went to bed approximately 1-3 h local time earlier during the first few days and were very sleepy compared to the week before the flight. There was a significant increase in the number of awakenings and in the feeling of 'not being at all rested' in the mornings. After the return flight eastwards, the subjects were very sleepy on the first evening but slept rather well for about 11 h. During the three following days, sleep restlessness, difficulties in falling asleep, and the feelings of sleepiness in the mornings increased compared to the week before the flights. Four days after the return flight, sleep length and the quality of sleep were, on average, the same as before the flights. According to the SCSB method, there were only small changes in the autonomic sleep phases due to the flights. After the westward flight, quiet sleep increased and intermediate sleep decreased compared to the sleep before the flight. The results indicate that most flight attendants have significant disturbances in sleep quality after transmedian flights. Sleep disturbances increase after both westward and eastward transmedian flights, but differ from each other in specific features.