Signal et al. conducted research into the sleep of flight crews of ultra-long haul flights , measuring their sleep when in-flight in the crew rest periods against their sleep when on a layover in a hotel on the ground.
This article summarises and analyses the results of this research.
The study analysed the sleep during crew rest periods of pilots making aircraft delivery flights from the USA to Asia, in addition to analysis of the crew sleep in their layover hotel.
Quantitative research into the quality and duration of in-flight crew rest on ultra-long haul flights.
Sample group comprised of 21 long haul pilots, comprised of 11 captains (mean age 48 years) and 10 First Officers (mean age 35 years). All participants were male.
Data was analysed to identify the time in bed, total sleep duration, the time spent in each sleep stage, during the 2 crew rest locations.
Study confirms that crew rest in flight is inferior to the rest achieved on the ground. Total sleep duration is reduced, and an increased percentage of the sleep achieved is spent in the lighter stages of sleep (stages 1 and 2). A significant reduction in the percentage of REM sleep is demonstrated in the data from the in-flight crew rest, as well as an increase in the amount of time spent awake after the first onset of sleep, with sleep stage transitions as well as more awakenings.
Data was gathered across a small number of sleep sessions so results can be extrapolated to apply to the wider long haul pilot community; however the margin of error will be high due to the limited scope of the collected data set.
|Comparison between Hotel sleep and In-flight sleep (mean)|
|Time in bed & Total sleep time measured in hours||Transitions and Awakenings given per hour||Percentage of Total sleep time|
|Time in bed||Total sleep time||Sleep stage transitions||Awakenings||Awake after sleep onset||Sleep efficiency|
Illustration 1. shows that In-flight sleep was shorter in duration and more disturbed, with more sleep transitions and relative amount of time spent awake after first onset of sleep. A reduction in sleep efficiency when compared to the Hotel sleep is also evident.
|Comparison between measured sleep stages in Hotel sleep and In-flight sleep|
|Hotel sleep||In-flight sleep|
|Stage 1 sleep||16.7%||6.5||23.8%||10.3||0.010||Highly significant|
|Stage 2 sleep||58.0%||7.2||62.7%||9.0||0.025||Significant|
|Stage 3 sleep||1.0%||(0 - 6.8)**||0.5%||(0 - 6.1)**||0.035||Significant|
|REM sleep||21.1%||5.9||12.7%||8.7||0.001||Very highly significant|
|*Sleep stages given as a percentage of Total sleep time|
|** SD given as a range where appropriate|
|*** Stage 4 sleep omitted for clarity (Hotel sleep mean = 0%, In-flight sleep = none measured).|
Illustration 2. shows that the light stages of sleep (stage 1 & stage 2) represented more of the sleep experienced in-flight that the crews sleep on the ground (86.5% in-flight vs. 74.7% on ground). While this difference is significant the difference between REM sleep was more so, (12.7% vs. 21.1%, P 0.001). REM sleep has been identified as of particular importance due to its psychological restorative effects, and thus the lack of REM sleep achieved during the in-flight crew rest is likely to have a negative cognitive impact on resultant crew performance, when compared to performance after crew rest on the ground.
The broader standard deviation range exhibited in the in-flight sleep indicates that the disruption to rest was more highly variable amongst individuals than the hotel rest periods.