Table 4.

Participant characteristics and quality of sleep

	Sleep disturbances					Use of sleeping medication					Daytime dysfunction					PSQI-global score
	No-risk group		Risk group			No-risk group		Risk group			No-risk group		Risk group			No-risk group		Risk group
	n	%	n	%	p	n	%	n	%	p	n	%	n	%	p	n	%	n	%	p
Sex
Male	153	53.5	133	46.5	0.962	289	99.0	3	1.0	0.298	153	54.4	128	45.6	0.626	248	95.0	13	5.0	0.610
Female	160	53.7	138	46.3		302	99.7	1	0.3		152	52.4	138	47.6		251	94.0	16	6.0
Family composition
Single-parent household	20	48.8	21	51.2	0.521	41	97.6	1	2.4	0.160	19	48.7	20	51.3	0.542	27	84.4	5	15.6	0.009
Two-parent household	293	54.0	250	46.0		550	99.5	3	0.5		286	53.8	246	46.2		472	95.2	24	4.8
Annual household income (¥)
< 3,000,000	18	40.9	26	59.1	0.116	43	97.7	1	2.3	0.187	21	48.8	22	51.2	0.329	30	85.7	5	14.3	0.098
3,000,000–6,000,000	132	56.7	101	43.3		239	98.8	3	1.2		114	49.8	115	50.2		200	93.9	13	6.1
6,000,000–9,000,000	81	49.1	84	50.9		166	100.0	0	0.0		94	58.8	66	41.3		141	95.9	6	4.1
≥ 9,000,000	76	57.6	56	42.4		133	100.0	0	0.0		70	54.3	59	45.7		118	95.9	5	4.1
Mother’s educational background
Middle school or high school	47	46.1	55	53.9	0.047	104	97.2	3	2.8	0.011	47	46.1	55	53.9	0.153	77	89.5	9	10.5	0.091
Junior college or vocational school	139	59.4	95	40.6		237	100.0	0	0.0		118	52.4	107	47.6		197	95.6	9	4.4
University or graduate school	124	51.0	119	49.0		245	99.6	1	0.4		137	57.3	102	42.7		220	95.2	11	4.8
Father’s educational background
Middle school or high school	77	58.3	55	41.7	0.441	134	98.5	2	1.5	0.073	64	49.2	66	50.8	0.394	106	93.0	8	7.0	0.492
Junior college or vocational school	36	49.3	37	50.7		73	98.6	1	1.4		37	51.4	35	48.6		63	95.5	3	4.5
University or graduate school	193	53.8	166	46.2		364	100.0	0	0.0		195	55.9	154	44.1		316	95.8	14	4.2

χ² analysis. Bold numbers indicate statistically significant differences