Sleep characteristics, sleep problems, and associations of self-efficacy among German university students

Figures & data

Table 1 Time going to bed among university students

Go to bed at	Frequency	Percentage
8 pm	3	0.2
9 pm	17	0.8
10 pm	187	8.5
11 pm	682	31.1
12 am	721	32.8
1 am	374	17.0
2 am	157	7.1
3 am	40	1.8
4 am	7	0.3
5 am	6	0.3

Table 2 Time needed to fall asleep in the gender adjusted overall sample and split in genders

Time needed to fall asleep	Overall sample		Female students		Male students		Differences between the genders
	Frequency	Proportion	Frequency	Proportion	Frequency	Proportion
Immediately	533	24.3%	375	24.0%	155	24.6%	–
15 min	760	34.6%	494	31.6%	238	37.7%	χ² = 7.553; P = 0.006
30 min	553	25.2%	427	27.3%	146	23.1%	χ² = 4.073; P = 0.044
1 h	226	10.3%	168	10.7%	62	9.8%	–
1.5 h	74	3.4%	59	3.8%	19	3.0%	–
2 h	37	1.7%	33	2.1%	8	1.3%	–
3 h	10	0.5%	7	0.4%	3	0.5%	–
>3 h	1	0.1%	2	0.1	–	–	–

Table 3 Short and long sleep and associations with prevalence of insomnia

	Average sleep duration (min)	Prevalence of insomnia
		Short sleepers (<1 SD)	Normal sleepers	Long sleepers (>1 SD)
Overall sample (gender adjusted)	M = 456.00	52/265	105/1676	13/255	χ² = 59.998;
	(SD = 70.84)	19.6%	6.3%	5.1%	P = 0.000
Males	M = 450.31	17/84	21/434	1/113	χ² = 35.439;
	(SD = 68.62)	20.2%	4.8%	0.9%	P = 0.000
Females	M = 461.66	32/170	97/1166	16/229	χ² = 21.131;
	(SD = 72.57)	18.8%	8.3%	7.0%	P = 0.000

Abbreviations: M, mean; SD, standard deviation.

Table 4 Time getting up and associations with prevalence of insomnia

Classification	Get up time	Frequency	Percentage	Prevalence of insomnia
Early	5 am	17	0.8	58/927
	6 am	271	12.3	6.3%
	7 am	638	29.1
Normal	8 am	652	29.7	76/1026
	9 am	375	17.1	7.4%
Late	10 am	133	6.0	36/242
	11 am	66	3.0	14.9%
	12 pm	30	1.4
	After 12 pm	14	0.6

Table 5 Logistic regression models evaluating the association between insomnia and previously introduced variables

Predictor variables	OR (95% CI) for insomnia	Adj OR (95% CI) for insomnia
	Univariate logistic regression models (unadjusted estimates)	Minimal multivariate logistic regression models (gender-adjusted estimates)	Multivariate logistic regression model of all variables
Gender	1.55 (1.08–2.24)*	–	1.37 (0.92–2.04)
Long-term student	1.62 (0.87–3.03)	1.66 (0.89–3.11)	1.96 (0.99–3.90)
Late riser	2.32 (1.56–3.45)**	2.45 (1.64–3.66)**	3.60 (2.19–5.91)**
Going to bed after midnight	1.34 (0.96–1.88)	1.46 (1.04–2.06)*	0.71 (0.46–1.09)
Sleeping short (<1 SD)	3.20 (2.24–4.57)**	3.29 (2.30–4.71)**	3.48 (2.29–5.30)**
Fitful sleep (3×/week)	6.10 (4.34–8.57)**	6.00 (4.27–8.44)**	4.37 (3.03–6.28)**

Notes:

* Statistically significant at P < 0.05;

** statistically significant at P < 0.01.

Abbreviations: adj OR, adjusted odds ratio; CI, confidence interval; OR, odds ratio.