Table 1.

Sleep habits shown as means (hh:mm/day) and standard deviations (SD) among Finnish school-aged children (n = 337–353)†

	2006		2008		∆ 2006–2008
	4th and 5th graders		5th and 6th graders
Girls (n = 177–181) †	mean	SD	mean	SD	mean	SD
Bedtime school day	21:29	0:37	21:48	0:37	0:23***	0:36
Wake-up time school day	7:10	0:26	7:01	0:25	−0:10***	0:30
Bedtime weekend	22:18	0:48	22:44	0:48	0:26***	0:47
Wake-up time weekend	8:42	0:53	9:08	0:59	0:27***	0:52
Discrepancy of bedtimes	0:53	0:35	0:56	0:38	0:04	0:42
Sleep duration school day	9:48	0:40	9:13	0:43	−0:32***	0:46
Sleep duration weekend	10:24	0:57	10:24	1:00	0:01	1:04
Discrepancy in sleep duration	0:39	0:58	1:12	1:00	0:33***	1:07
Boys (n = 159–172) †
Bedtime school day	21:24	0:41	21:41	0:39	0:18***	0:39
Wake-up time school day	7:06	0:30	7:07	0:25	0:00	0:35
Bedtime weekend	22:24	0:50	22:51	0:59	0:27***	0:48
Wake-up time weekend	8:27	1:08	8:54	1:10	0:27***	1:01
Discrepancy of bedtimes	1:01	0:41	1:11	0:47	0:09*	0:47
Sleep duration school day	9:42	0:48	9:25	0:44	−0:18***	0:48
Sleep duration weekend	10:03	1:12	10:03	1:08	0:00	1:15
Discrepancy in sleep duration	0:20	1:13	0:37	1:08	0:18**	1:13
All (n = 337–353) †
Bedtime school day	21:25	0:39	21:48	0:38	0:20***	0:37
Wake-up time school day	7:08	0:28	7:03‡	0:25	−0:05**	0:32
Bedtime weekend	22:21	0:49	22:48	0:54	0:26***	0:47
Wake-up time weekend	8:35‡	1:01	9:01‡	1:05	0:27***	0:57
Discrepancy of bedtimes	0:57	0:38	1:04‡‡	0:44	0:06*	0:44
Sleep duration school day	9:43	0:44	9:19‡‡	0:44	−0:25***	0:47
Sleep duration weekend	10:14‡‡	1:05	10:14‡‡	1:05	0:00	1:10
Discrepancy in sleep duration	0:30‡‡	1:06	0:55‡‡‡	1:06	0:26***	1:10

† Range of respondents in the analyses.

Difference between study years *** ≤0.001, **≤0.01 *≤0.05, paired sample t-test.

Difference between gender within years ‡‡‡≤0.001, ‡‡≤0.01, ‡≤0.05, independent-samples t-test.