A. Lowden et T. Akerstedt, Eastward long distance flights, sleep and wake patterns in air crews in connection with a two-day layover, J SLEEP RES, 8(1), 1999, pp. 15-24
The present study describes the spontaneous sleep/wake pattern in connectio
n with an eastward (Stockholm to Tokyo, + 8 h) transmeridian flight and sho
rt (51 h) layovers. To describe all sleep episodes and the recovery process
across 4 days, and to relate adjustment to individual differences, 49 Scan
dinavian Airlines System (SAS) air crew were monitored for 9 days with acti
vity 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. Napp
ing was common during the extended periods of wakefulness, particularly dur
ing flights. During the recovery days, ease of rising from sleep in the mor
nings was difficult throughout, and feelings of not being refreshed returne
d to baseline levels on the third recovery sleep. Elevated daytime sleepine
ss (24% of the day) was observed on the first recovery day. No individual d
ifferences related to gender, age or position (cabin/pilot) was found in sl
eep 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 wi
th air crew scheduling. Comparisons with a westbound flight showed the east
bound flight layover sleep to be more problematic and containing more nappi
ng.