Factors

Sleep duration before school days

Non-school day catch-up sleep duration

Total

<0

0 (Reference)

0 - 1

1 - 2

>2 hrs.

Number (%)

≤7 hrs.

44 (1.6%)

217 (8.0%)

359 (13.2%)

280 (10.3%)

304 (11.2%)

1204 (44.2%)

7 hrs.<

135 (5.0%)

495 (18.2%)

561 (20.6%)

240 (8.8%)

87 (3.2%)

1518 (55.8%)

Grade

≤7 hrs.

9.2, 1.8

9.4, 1.7

9.3, 1.8

9.2, 1.8

9.4, 1.8

9.3, 1.8

7 hrs.<

6.9, 1.7

6.6, 1.5

6.7, 0.7

6.7, 1.5

7.1**, 2.0

6.7, 1.6

P value

<0.01

<0.01

<0.01

<0.01

<0.01

<0.01

Gender (male = 1, female = 2)

≤7 hrs.

1.3, 0.5

1.4, 0.5

1.5**, 0.5

1.5**, 0.5

1.6**, 0.5

1.5, 0.5

7 hrs.<

1.3**, 0.5

1.4, 0.5

1.5**, 0.5

1.6**, 0.5

1.6**, 0.5

1.5, 0.5

P value

0.05<

0.05<

0.05<

0.05<

0.05<

0.05<

Bedtime before school days

≤7 hrs.

23.8, 1.0

23.6, 0.9

23.7, 0.9

23.9**, 0.9

24.2**, 1.0

23.9, 0.9

7 hrs.<

21.7, 0.9

21.8, 0.7

22.1**, 0.7

22.3**, 0.6

22.3**, 0.7

22.0, 0.7

P value

<0.01

<0.01

<0.01

<0.01

<0.01

<0.01

Bedtime before non-school days

≤7 hrs.

24.9**, 1.2

24.0, 1.1

23.9, 1.2

24.0, 1.2

24.3**, 1.3

24.1, 1.2

7 hrs.<

22.7**, 1.1

22.3, 0.9

22.4, 0.9

22.5, 0.9

22.5, 1.0

22.4, 0.9

P value

<0.01

<0.01

<0.01

<0.01

<0.01

<0.01

Waking time on school days

≤7 hrs.

6.1, 0.7

6.1, 0.7

6.2, 0.8

6.4**, 0.7

6.3**, 0.7

6.3, 0.7

7 hrs.<

6.7*, 0.7

6.5, 0.5

6.5, 0.5

6.6, 0.5

6.6, 0.6

6.6, 0.5

P value

<0.01

<0.01

<0.01

<0.01

<0.01

<0.01

Waking time on non-school days

≤7 hrs.

6.1, 0.8

6.5, 1.0

7.4**, 1.1

8.5**, 1.1

9.9**, 1.3

8.1, 1.7

7 hrs.<

6.4**, 0.9

7.0, 0.8

7.8**, 0.8

8.7**, 0.8

10.0**, 1.1

7.7, 1.2

P value

<0.05

<0.01

<0.01

<0.01

0.05<

<0.01

Sleep duration before non-school days (hrs.)

≤7 hrs.

5.2**, 1.0

6.5, 0.7

7.5**, 0.7

8.5**, 0.7

9.6**, 1.1

8.0, 1.5

7 hrs.<

7.7**, 0.8

8.7, 0.6

9.4**, 0.5

10.3**, 0.5

11.5**, 0.7

9.3, 1.1

P value

<0.01

<0.01

<0.01

<0.01

<0.01

<0.01

Averaged sleep duration a day (hrs.)

≤7 hrs.

6.0**, 0.8

6.5, 0.7

6.8**, 0.7

7.1**, 0.7

7.1**, 0.8

6.9, 0.8

7 hrs.<

8.6, 0.8

8.7, 0.6

8.7, 0.6

8.8**, 0.5

9.2**, 0.5

8.8, 0.6

P value

<0.01

<0.01

<0.01

<0.01

<0.01

<0.01

Social jetlag (hrs.)

≤7 hrs.

0.6, 0.6

0.4, 0.7

0.7**, 0.7

1.1**, 0.7

1.8**, 0.8

1.0, 0.9

7 hrs.<

0.3, 0.9

0.5, 0.6

0.8**, 0.6

1.2**, 0.6

1.8**, 0.7

0.8, 0.7

P value

0.05<

p<0.05

0.05<

0.05<

0.05<

<0.01

Self-reported academic performance (1, very good, …, 4, poor)

≤7 hrs.

2.7, 0.9

2.6, 0.8

2.5, 0.8

2.6, 0.9

2.6, 0.8

2.6, 0.8

7 hrs.<

2.4, 0.8

2.3, 0.8

2.3, 0.8

2.3, 0.7

2.6**, 0.8

2.3, 0.8

P value

NS

<0.01

<0.01

<0.01

0.05<

<0.01

Standardized BMI

≤7 hrs.

0.3, 1.4

0.1, 1.0

0.0, 0.9

0.0, 1.0

0.0, 1.0

0.0, 1.0

7 hrs.<

0.0, 1.1

0.0, 1.0

−0.1, 1.0

−0.1, 0.9

−0.1, 1.1

0.0, 1.0

P value

0.05<

0.05<

0.05<

0.05<

0.05<

0.05<

Sleepiness during class (1, never, …, 4, always)

≤7 hrs.

2.5, 0.9

2.3, 0.9

2.3, 0.8

2.2, 0.9

2.4, 0.9

2.3, 0.9

7 hrs.<

1.8, 0.7

1.7, 0.7

1.7, 0.7

1.8, 0.6

2.0**, 0.7

1.7, 0.7

P value

<0.01

<0.01

<0.01

<0.01

<0.01

<0.01

After-school activity (hrs./week)

≤7 hrs.

9.5, 10.2

7.9, 10.1

8.3, 9.1

7.2, 8.0

6.6, 8.1

7.6, 8.9

7 hrs.<

6.6*, 6.6

5.1, 6.3

4.2, 5.0

3.7**, 4.9

4.4, 5.9

4.6, 5.7

P value

0.05<

<0.01

<0.01

<0.01

<0.01

<0.01

Physical activity (days/week)

≤7 hrs.

4.5, 2.7

4.3, 3.0

3.5**, 3.1

2.9**, 3.0

2.0**, 2.7

3.2, 3.1

7 hrs.<

4.1*, 2.6

3.4, 2.7

2.9, 2.7

2.5**, 2.7

2.7, 2.8

3.1, 2.7

P value

0.05<

<0.01

<0.01

0.05<

<0.05

0.05<

Breakfast taking (1, always, …, 4, never)

≤7 hrs.

1.6, 0.8

1.3, 0.7

1.2, 0.6

1.3, 0.6

1.4, 0.7

1.3, 0.7

7 hrs.<

1.2, 0.5

1.1, 0.4

1.1, 0.4

1.1, 0.5

1.3**, 0.7

1.1, 0.4

P value

<0.01

<0.01

<0.01

<0.05

0.05<

<0.01

Defecation frequency (1. every day,….4, twice a week or less)

≤7 hrs.

1.7, 1.0

1.5, 0.8

1.6, 0.9

1.7, 0.9

1.7, 0.9

1.7, 0.9

7 hrs.<

1.6, 0.8

1.6, 0.8

1.6, 0.9

1.6, 0.8

2.0**, 1.0

1.6, 0.9

P value

0.05<

0.05<

0.05<

0.05<

<0.05

0.05<

Averaged screen time a day (hrs.)

≤7 hrs.

4.1**, 2.5

2.9, 1.9

2.9, 1.9

3.1, 1.7

3.6**, 2.0

3.2, 1.9

7 hrs.<

2.4, 1.5

2.2, 1.9

2.5**, 1.5

2.6**, 1.5

2.9**, 1.7

2.5, 1.5

P value

<0.01

<0.01

<0.01

<0.01

<0.01

<0.01