Table 3.

Characteristics and sleep on school days and non-school days at age 15 and 17 of students attending traditional and college-style schedule schools at age 17.

		Traditional Schedule (N=61, 77% Female)				College-Style Schedule (N=84, 53.6% Female)				Traditional Vs College-style
		15y old	17y old	p (15 vs 17)		17y old	17y old	p (15 vs 17)		p (15y)	p (17y)
Characteristics
	Parent with university degree, N (%)		47 (77%)				56 (67%)				0.24
	Organized sports participation, N (%)	48 (79%)	31 (51%)	< 0.001		53 (63%)	37 (44%)	0.005		0.1	1.0
	National English exama,b,c	35.76 ± 8.09				33.09 ± 9.19				0.14
	National Icelandic exama,b,d	38.69 ± 7.85				31.97 ± 8.22				<0.001
	National mathematics exama,b,e	38.25 ± 7.67				31.63 ± 8.56				<0.001
School Nights
	Time in bed, h/day	7.2 ± 0.7	6.7 ± 0.8	<0.001		7.0 ± 0.8	6.9 ± 0.9	1.0		0.3	0.9
	Mid-sleep time, clock time ± min	03:42 ± 31.8	03:54 ± 40.4	0.2		03:59 ± 37.6	04:38 ± 60.4	<0.001		0.1	<0.001
	WASO, min/night	47.7 ± 18.7	45.0 ± 17.4	1.0		49.1 ± 23.4	50.3 ± 23.4	1.0		1.0	0.5
	Awakenings, number/night	18.5 ± 4.7	17.2 ± 4.5	0.2		18.0 ± 5.8	18.4 ± 6.2	1.0		1.0	0.8
	Sleep efficiency, %	88.7 ± 3.8	88.6 ± 4.3	1.0		88.1 ± 4.7	87.5 ± 5.2	0.8		1.0	0.6
	Time in bed variability, min	47.4 ± 36.0	65.8 ± 48.9	0.04		54.7 ± 33.8	84.7 ± 45.1	<0.001		0.9	0.02
	Sleep time variability, min	44.8 ± 31.4	57.5 ± 42.4	0.2		49.2 ± .6.5	77.2 ± 42.7	<0.001		1.0	0.002
	Bed time variability, min	40.6 ± 32.5	41.8 ± 26.1	1.00		48.2 ± 33.6	53.8 ± 26.2	0.7		0.7	0.11
	Rise time variability, min	27.7 ± 21.6	42.3 ± 37.5	0.2		46.8 ± 49.0	67.3 ± 44.6	0.003		0.02	0.001
	Recorded nights, N	4.7 ± 0.6	5.3 ± 0.7	<0.001		4.’ ± 0.6	5.3 ± 0.7	<0.001		1.0	1.0
	Valid nights, N	4.7 ± 0.6	5.2 ± 0.8	<0.001		4.6 ± 0.6	5.2 ± 0.8	<0.001		1.0	1.0
	Invalid nights, N	0.03 ± 0.26	0.02 ± 0.15	0.6		0.08 ± 0.38	0.07 ± 0.26	0.5		1.0	1.0
Non-school Nights
	Time in bed, h/day	8.4 ± 1.2	7.8 ± 1.2	0.053		8.3 ± 1.5	7.8 ± 1.4	0.01		1.0	1.0
	Mid-sleep time, clock time ± min	05:31 ± 59.1	06:08 ± 70.6	0.003		06:03 ± 64.4	06:27 ± 83.3	0.04		0.04	0.6
	WASO, min	58.87 ± 25.7	50.0 ± 20.1	0.1		60.1 ± 29.7	54.8 ± 27.5	0.5		1.0	1.0
	Awakenings, number/night	22.2 ± 7.6	19.6 ± 6.4	0.1		21.8 ± 8.5	20.8 ± 8.0	1.0		1.0	1.0
	Sleep efficiency, %	88.2 ± 4. 7	88.8 ± 4.6	1.0		87.9 ± 5.2	88.2 ± 5.1	1.0		1.0	1.0
	Recorded nights, N	2. ± 0.6	2.0 ± 0.3	<0.001		2.5 ± 0.6	2.0 ± 0.3	<0.001		0.4	1.0
	Valid nights, N	2.6 ± 0.7	2.0 ± 0.3	<0.001		2.5 ± 0.6	2.0 ± 0.4	<0.001		0.9	1.0
	Invalid nights, N	0.02 ± 0.13	0.02 ± 0.13	1.0		0.02 ± 0.15	0.04 ± 0.19	1.0		0.9	1.0

Results are means ± standard deviation; All comparisons corrected for sex, parental education, and multiple comparisons; WASO = minutes of wakening after sleep onset;

^aNationally normalized (mean = 30, standard deviation = 10, maximum score = 60); National test scores available for:

^b55 traditional schedule students (13 boys, 42 girls),

^c74 college-style schedule students (36 boys, 38 girls),

^d74 college-style schedule students (34 boys, 40 girls),

^e71 college-style schedule students (36 boys, 35 girls).