Patterns of sleep-wakefulness before and after transmeridian flight in commercial airline pilots

This study investigated changes in sleep-wake rhythms due to time zone changes. The subjects were 12 commercial airline cockpit crewmembers on active duty who spent their baseline nights in a sleep facility in Tokyo. After flying from Tokyo to San Francisco, they underwent two consecutive nights of sleep polysomnography and daytime sleep latency tests (MSLTs). During the San Francisco layover, slight changes in sleep quality were observed. REM sleep (%) was decreased, while slow wave sleep (%) tended to increase during the major sleeps. Subjective sleep quality assessments also exhibited a decrease in comparison to the baseline values. Daytime sleepiness as measured by MSLTs was generally greater in the latter half of the awake period during layover as compared with baseline. When the subjects were divided into "morning" or "evening" types, the daytime MSLTs of each type showed different patterns. The former displayed a decreasing L-shaped trend, while the latter showed a pronounced W-shaped pattern. These results suggest that further investigation of the individual differences in circadian phase position may be important for understanding the effects of multiple time zone flights.