Crew Factors in Flight Operations I: Effects of 9-Hour Time Zone Changes on Fatigue and the Circadian Rhythms of Sleep/Wake and Core Temperature

Gander, P. H., Myhre, G., Graeber, R. C., Anderson, H. T., Lauber, J. K. (1985).
Crew Factors in Flight Operations I: Effects of Nine-Hour Time-Zone Changes on Fatigue and Circadian Rhythms of Sleep/Wake and Core Temperature
(NASA Technical Memorandum 88197). Moffett Field, California: NASA Ames Research Center.

Physiological and psychological disruptions caused by transmeridian flights may affect the ability of flight crews to meet operational demands. To study these effects, 9 Royal Norwegian Airforce P3-Orion crewmembers flew from Norway to California (-9 hr), and back (+9 hr). Rectal temperature, heart rate and wrist activity were recorded every 2 min, fatigue and mood were rated every 2 hr during the waking day, and logs were kept of sleep times and ratings. Subjects also completed 4 personality inventories.

The time-zone shifts produced negative changes in mood which persisted longer after westward flights. Sleep quality (subjective and objective) and duration were slightly disrupted (more after eastward flights). The circadian rhythms of sleep/wake and temperature adjusted more slowly. the size of the delay shift was significantly correclated with scores on extraversion and achievement need personality scales. Responses to the 9-hr advance were more variable. One subject exhibited a 15-hr delay in his temperature rhythm, and an atpyical sleep/nap pattern. On average, the sleep/wake cycle (but not the temperature rhythm), completed the 9-hr advance by the end of the study. Both rhythms adapted more slowly after the eastward flight.