Sleep and wake patterns in aircrew on a 2-day layover on westward long distance flights.

BACKGROUND

As part of a research program of sleep/wake disturbances in connection with irregular work hours and time zone transitions, the study aimed to describe the spontaneous sleep/wake pattern in connection with a westward (Stockholm to Los Angeles) transmeridian flight (-9 h) and short layover (50 h).

HYPOTHESIS

To describe all sleep episodes and the recovery process across 4 d, and to relate adjustment to individual differences.

METHODS

We monitored 42 SAS aircrew for 9 d with activity monitors and diary before, during, and after flight.

RESULTS

During the outbound day the wake span was 21.7 h and 90% of the aircrew adopted local bed times on layover. The readaptation to normal sleep/wake patterns were rapid on the return. Napping was common (93%), especially on-board and before the return. Sleep efficiency dropped below 90% during layover, being felt to be too short and disturbed by awakenings, and gradually returned to normal across four recovery days. Recovery sleep was characterized by difficulties waking up and feelings of not being refreshed from sleep. Sleepiness symptoms increased during layover and gradually decreased across recovery days, still being elevated on day 4.

CONCLUSIONS

In the present study we found that westward flights are associated with extended wake spans during layover, increased sleepiness, and slow recovery on return home. Strategic sleeping may counteract the effect somewhat, but individual differences are few.