Table 1

Basic information, sociodemographic characteristics and lifestyle characteristics

Variables	Normal-sleep quality group (n=160)	Low-sleep quality group (n=138)	χ²	P value	Effect size	95% CI
Variables	Normal-sleep quality group (n=160)	Low-sleep quality group (n=138)	χ²	P value	Effect size	Lower	Upper
Age (years)	20.8±1.4	20.7±1.3		0.666	−0.025	0.000	0.000
Age at menarche (years)	12.5±1.7	12.5±1.5		0.839	0.012	0.000	0.000
Body mass index (kg/m²)	20.5±2.6	20.8±2.6		0.884	0.008	−0.521	0.459
Part-time job
Yes	135 (84.4)	123 (89.1)	1.442	0.230	0.070	0.004	0.168
No	25 (15.6)	15 (10.9)
Living status
Alone	57 (35.6)	46 (33.3)	0.172	0.678	0.024	0.002	0.143
With others	103 (64.4)	92 (66.7)
Alcohol intake
Low	145 (90.6)	129 (93.5)	0.815	0.367	0.052	0.003	0.169
High	15 (9.4)	9 (6.5)
Smoking
No	152 (95.0)	133 (96.4)	0.337	0.562	0.034	0.002	0.149
Yes	8 (5.0)	5 (0.6)
Breakfast
Eating	114 (71.3)	81 (58.7)	5.163	0.023*	0.132	0.016	0.245
Not eating	46 (28.7)	57 (41.3)
Eating between meals
Eating	101 (63.1)	95 (68.8)	1.075	0.300	0.060	0.004	0.172
Not eating	59 (36.9)	43 (31.2)
Caffeine consumption (≥3 times/week)
Yes	74 (46.3)	57 (41.3)	0.736	0.391	0.050	0.031	0.234
No	86 (53.7)	81 (58.7)
Studying until going to bed (≥3 times/week)
Yes	37 (23.1)	32 (23.2)	0.000	0.990	0.001	0.016	0.183
No	123 (76.9)	106 (76.8)
Watching TV until going to bed (≥3 times/week)
Yes	44 (27.5)	29 (21.0)	1.685	0.194	0.075	0.023	0.206
No	116 (72.5)	109 (79.0)
Screen time
Leisure (min/day)	256.4±204.2	252.1±144.0		0.578	0.032	−30.000	30.000
Study (min/day)	105.9±129.8	107.1±124.4		0.265	0.064	−20.000	0.000