Circadian urinary 6-sulphatoxymelatonin, cortisol excretion and locomotor activity in airline pilots during transmeridian flights

Airline pilots divided into two groups of age lover and under 50 years) wer e studied before, during and after westbound (Madrid-Mexico City-Madrid, n = 12) and eastbound (Madrid-Tokyo-Madrid, n = 21) flights. A group of 10 ag e-matched people staying in Madrid were submitted to the same tests and ser ved as a control group. Changes in urinary 6-sulphatoxymelatonin (6-aMTs) a nd free cortisol excretion (determined in 6-hr intervals) were measured by radioimmunoassay. Using wrist actigraphy, the circadian locomotor activity rhythm (LAR) was also monitored. Maximal baseline excretion of 6-aMTs occur red between 00:00 and 12:00 hr and maximal excretion of cortisol took place between 6:00 and 12:00 hr in the control group. Analysed globally, older p ilots exhibited significantly lower values of 6-aMTs than younger ones. In both flight directions, pilots maintained the pattern of excretion of 6-aMT s, corresponding to baseline. The return flight to Madrid from Mexico and T okyo coincided with a maximum in 6-aMTs excretion. Pilots kept the cortisol pattern found in the control group, with those over 50 years of age exhibi ting significantly lower cortisol values than the younger ones. A 7-hr dela y in acrophase of LAR after 2 days in Mexico City was found after cosinor a nalysis, and similar pre-flight values were found after returning to Madrid . An 8-9-hr acrophase advance of LAR was observed after arriving in Tokyo, with acrophase on the post-return flight day still being advanced 34 hr as compared to pre-flight values. Decreases in the amplitude of LAR in older p ilots were found at Mexico City, as well as at Tokyo stopover and on post-f light day. Data confirm the occurrence of internal desynchronization in air line crewmembers after transmeridian flights.