| |
Junior (1–3)
|
Senior (4–6)
| |
|---|
|
Total n = 1663
|
n = 826 (%)
|
n = 837 (%)
|
P value
|
|---|
|
Sex (boy)
|
50.1
|
49.6
|
0.83
|
|
Wakeup time on week day
|
|
< 6:30 a.m.
|
52.8
|
48.6
|
0.07
|
|
6:30 to < 7:00
|
44.2
|
46.6
| |
|
≥ 7:00
|
3.0
|
4.8
| |
|
Skipping breakfast (yes)
|
4.5
|
8.7
|
< 0.001
|
|
Screen time on week day (≥ 2 h)
|
34.5
|
43.2
|
< 0.001
|
|
Physical activity
|
|
Very often
|
28.3
|
28.7
|
< 0.001
|
|
Often
|
48.8
|
39.7
| |
|
Rarely
|
22.9
|
31.7
| |
|
Bedtime on week day
|
|
< 10 p.m.
|
88.6
|
53.7
|
< 0.001
|
|
10 to < 10:30
|
9.2
|
31.2
| |
|
10:30 or later
|
2.2
|
15.2
| |
|
Daytime sleepiness (yes)
|
12.8
|
20.9
|
< 0.001
|
|
Obesity (yes)
|
8.2
|
7.8
|
0.73
|
|
Cram school (yes)
|
23.0
|
27.0
|
0.06
|
|
Study duration at home (< 1 h)
|
74.8
|
50.3
|
< 0.001
|
|
Paternal smoke (yes)
|
42.1
|
46.2
|
0.09
|
|
Maternal smoke (yes)
|
10.2
|
11.7
|
0.32
|
|
Subjective SES
|
|
High
|
28.3
|
26.9
|
0.73
|
|
Middle
|
47.8
|
47.9
| |
|
Low
|
23.8
|
25.2
| |
|
Subjective academic performance
| | |
0.20
|
|
Well or relatively well
|
82.4
|
81.6
| |
|
Neither
|
11.9
|
14.1
| |
|
Relatively poor or poor
|
5.7
|
4.3
| |
- Pearson chi-square test
- SES, socioeconomic status
