TABLE 2.

Average sleep duration and architecture during each study period¹

	8.5-h bedtime	5.5-h bedtime	Change 5.5–8.5-h bedtime
Total sleep time (h:min)	7:13 ± 0:26	5:11 ± 0:07	−2:02 ± 0:25
Lights-off time (h:min)	23:16 ± 00:39	0:31 ± 00:49	1:19 ± 0:25
Wakeup time (h:min)	7:42 ± 00:39	6:02 ± 00:49	−1:39 ± 0:24
Sleep onset latency (min)	20 ± 9	8 ± 3	−12 ± 8
Wake after sleep onset (min)	61 ± 24	14 ± 6	−46 ± 22
Sleep efficiency (%)	85 ± 5	94 ± 2	9 ± 5
Stage 1 sleep (min)	30 ± 15	16 ± 6	−14 ± 15
Stage 2 sleep (min)	246 ± 40	177 ± 44	−69 ± 29
Stages 3 + 4 sleep (min)	51 ± 37	45 ± 36	−6 ± 16
REM sleep (min)	106 ± 23	74 ± 22	−32 ± 22

¹All values are group means ± SD (n = 11). REM, rapid eye movement. P < 0.01 for all paired t test comparisons, except for stage 1 sleep (P = 0.01) and stages 3 + 4 sleep (P = 0.23).