Table 8.

Correlation between sleep quality, academic achievement and sleep habits/problems in the study sample.

	Variable	Sleep Quality		Academic achievement
		Correlation Coefficient	p	Correlation Coefficient	p
1.	Academic level	0.02	0.7	0.01	0.8
2.	Time of going to bed	0.2	< 0.01	0.08	0.1
3.	Usual time to wake up	0.06	0.2	0.01	0.8
4.	Duration of sleep	0.08	0.09	0.01	0.8
5.	Drinking coffee late at night	0.01	0.052	0.02	0.07
6.	Use of sleeping pills	0.04	0.5	0.01	0.08
7.	Time to fall asleep (latency)	0.23	< 0.01	0.06	0.3
8.	Frequency of nocturnal awakenings	0.15	< 0.01	0.03	0.6
9.	Snoring	0.05	0.3	0.01	0.8
10.	Waking up due to nocturnal noise	0.1	0.02	0.01	0.08
11.	Waking up because of nocturnal eating	0.04	0.4	0.01	0.8
12.	Sleep talking	0.01	0.9	0.1	0.05
13.	Sleepwalking	0.01	0.9	0.01	0.09
14.	Bruxism	0.01	0.9	0.03	0.5
15.	Nightmares	0.1	0.046	0.1	0.024
16.	Restless leg syndrome	0.01	0.8	0.06	0.2
17.	Feeling tired in the morning	0.25	< 0.01	0.01	0.8
18.	Daytime sleepiness	0.1	0.016	0.03	0.5
19.	Daytime sleepiness during lectures	0.2	< 0.01	0.07	0.2
20.	Daytime sleepiness during free time	0.01	0.8	0.02	0.7
21.	Daytime naps	0.01	0.8	0.01	0.9
22.	Sleep quality	-	-	0.02	0.7
23.	Academic achievement	0.02	0.7	-	-
24.	Leisure time	0.2	< 0.01	0.4	< 0.01
25.	Living conditions	0.1	0.04	0.24	< 0.01