Eastward long distance flights, sleep and wake patterns in air crews in connection with a two-day layover
The present study describes the spontaneous sleep/wake pattern in connection with an eastward (Stockholm to Tokyo,+8 h) transmeridian flight and short (51 h) layovers. To describe all sleep episodes and the recovery process across 4 days, and to relate adjustment to individual differences, 49 Scandinavian Airlines System (SAS) air crew were monitored for 9 days with activity monitors and sleep/wake diary before-during-after flight. The outbound flight involved a period of wakefulness extended to 21 h, frequently (87% of air crew) terminated by a long nap in Tokyo which was calm but difficult to wake up from. Then followed two night oriented sleep periods of normal length but of reduced efficiency, containing many and long awakenings. Napping was common during the extended periods of wakefulness, particularly during flights. During the recovery days, ease of rising from sleep in the mornings was difficult throughout, and feelings of not being refreshed returned to baseline levels on the third recovery sleep. Elevated daytime sleepiness (24% of the day) was observed on the first recovery day. No individual differences related to gender, age or position (cabin/pilot) was found in sleep strategy. Poor adjusters, subjects with a perceived lowered capacity on recovery days, showed more premature awakenings abroad and less refreshing sleep during the last 12 months, suggesting a decreased ability to cope with air crew scheduling. Comparisons with a westbound flight showed the eastbound flight layover sleep to be more problematic and containing more napping.