Table 2. Sleep characteristics among study participants by data collection period.

	L-11 mean (s.d.)	Flight mean (s.d.)
Actigraphy sleep duration (h)	5.9 (0.9)	6.1 (0.7)
Subjective sleep duration (h)	6.3 (0.8)	6.5 (0.7)
Latency (m)	14.4 (9.5)	13.7 (10.1)
Number of awakenings	1.3 (0.8)	1.5 (1.0)
Sleep efficiency*	87% (5%)	89% (5%)
Sleep quality	62.3 (15.6)	66.5 (13.4)
Alertness	56.0 (19.5)	57.7 (18.7)

^*The sleep efficiency was calculated from actigraphy as the time scored as sleep/the sleep period time.