Table 1.

Characteristics of the participants.

	M±SD or %			p
	Total	Girls	Boys
Age	14.8±1.2	14.8±1.2	14.8±1.2	0.311
Grade				0.002
8nd grade	60.9	58.6	63.6
10nd grade	39.1	41.4	36.4
Father education				< 0.001
No education	1.2	0.6	18.1
Primary school	1.8	19.8	17.7
Middle school	36.0	38.2	33.6
Secondary school	26.5	26.6	26.5
Superior education	17.4	14.8	20.4
Mother education				< 0.001
No education	0.9	0.3	1.6
Primary school	11.8	13.3	10.1
Middle school	35.9	37.2	34.3
Secondary school	29.2	28.6	29.9
Superior education	22.2	20.5	24.1
Sleep deprivation	13.1	14.3	11.7	0.026
Sleep less	13.9	14.3	13.4	0.503
Difficulties falling asleep	19.5	22.1	16.7	< 0.001
Waking up tired	50.8	53.4	47.9	0.001
Waking up middle of the night	9.1	10.3	7.7	0.007

Age was tested by Student t-test; education was tested by Chi square test; all other variables were tested by Fisher's exact test.