Urinary cortisol excretion and mood ratings in aircraft cabin crew during a tour of duty involving a disruption in circadian rhythm

A psychophysiological study was carried out on 28 cabin crew, comprising two teams, who were to travel from Sydney to Los Angeles and return, with stopovers in Los Angeles of 58 and 82 hr respectively. Every urine sample for a period of nine days, commencing 2 days before the flight, was collected. The volume and time the sample was passed were recorded so that urinary cortisol secretion rates could be calculated. Mood was also rated on a scale scored 0-9 at the same time the urine sample was collected. A control group matched for age, sex ratio, and degree of manual labour involved in their occupation, but not involved with the flights, was included in the study for comparison. On the basis of urinary cortisol excretion rates, the crews in Sydney before the flight and in Los Angeles were more highly stressed than the control group. The urinary cortisol excretion rates were significantly greater than those of the control group in Sydney before the flight, in Los Angeles, and during the return flight, but not on the flight on. The high excretion rates before the flight were attributed to an apprehension factor, whereas the elevated values in Los Angeles and during the flight back were attributed to a disruption in circadian rhythm. A factor analysis of mood ratings showed three major factors assessing vitality, distress, and relaxation. Analysis of variance of the mood ratings showed significant changes over the tour of duty for 13 of the 14 moods.