Table 1 The demographic characteristics and comparison of a low-IHS and high-IHS group following a median split, on PIU, sleep, internet usage time, twitter usage, and school performance

Total N (%)

 Male

χ² value 3.963

Male vs Female < 0.001

 Female

Age

19.34

1.10

19.44

1.13

19.26

1.08

2.900

0.004

Happiness (IHS)

30.60

6.53

25.12

4.47

35.52

3.44

−45.893

< 0.001

IAT

37.87

12.59

40.62

13.43

35.40

11.24

7.438

< 0.001

PSQI global score

5.88

2.52

6.48

2.54

5.33

2.38

8.269

< 0.001

Subjective sleep quality

1.13

0.71

1.26

0.71

1.02

0.69

6.154

< 0.001

Sleep latency

0.99

0.92

1.15

0.96

0.84

0.85

6.165

< 0.001

Sleep duration

1.69

0.98

1.74

0.97

1.66

0.99

1.477

0.140

Habitual sleep efficiency

0.21

0.56

0.25

0.61

0.17

0.50

2.415

0.016

Sleep disturbance

0.68

0.50

0.75

0.49

0.62

0.51

4.914

< 0.001

Use of sleeping medications

0.04

0.32

0.05

0.33

0.03

0.30

0.874

0.382

Daytime dysfunction

1.13

0.71

1.28

0.87

1.00

0.89

5.529

< 0.001

Internet usage time/ min (Weekday)

205.79

147.70

215.69

159.08

196.95

136.25

2.224

0.026

Internet usage time/ min (Weekend)

277.63

183.86

296.74

197.60

260.63

169.04

3.434

< 0.001

Number of Twitter follows

218.18

393.53

215.35

456.81

220.70

327.14

−0.239

0.811

Number of Twitter followers

256.73

1354.17

280.50

1859.24

235.53

623.13

0.584

0.559

Number of times skipping a whole day of school

1.26

.551

1.33

0.64

1.19

0.45

4.206

< 0.001

Number of times arriving late for school

1.33

.655

1.41

0.76

1.25

0.54

4.295

< 0.001