Table 1.

Sample characteristics by gender.

	ALL	Boy	Girl	P
Sample size	46639	23743 (50.9%)	22896 (49.1%)
Age	10.82±3.31	10.69±3.27	10.95±3.35	<0.001
Outdoor activity (%)
<1 h	37.5	34.4	40.7	<0.001
1–2 h	39.7	40.8	38.7
≥2 h	22.8	24.9	20.6
Insufficient sleep duration (%)	74.9	73.7	76.1	<0.001
6–13 years	68.2	67.6	68.8	0.022
14–17 years	96.4	95.1	97.5	<0.001
Sedentary	5.68±3.69	5.51±3.66	5.85±3.72	<0.001
6–13 years	5.25±3.49	5.18±3.49	5.32±3.49	<0.001
14–17 years	7.07±3.97	6.69±4.00	7.41±3.92	<0.001
Doing homework	1.92±1.21	1.87±1.19	1.97±1.23	<0.001
6–13 years	1.73±1.11	1.72±1.11	1.74±1.11	0.127
14–17 years	2.52±1.32	2.39±1.32	2.64±1.31	<0.001
Watching TV	0.91±1.02	0.95±1.04	0.87±1.00	0.01
6–13 years	0.95±0.96	0.99±1.00	0.90±0.91	<0.001
14–17 years	0.78±1.19	0.76±1.12	0.80±1.24	0.130
Playing computer game	0.68±1.09	0.79±1.22	0.58±0.93	<0.001
6–13 years	0.61±0.98	0.70±1.09	0.51±0.83	<0.001
14–17 years	0.93±1.37	1.10±1.56	0.78±1.16	<0.001
Urban/rural area (%)
Urban	62.1	61.8	62.4	0.181
Rural	37.9	38.2	37.6
BMI (kg/m2)	18.60±3.79	18.90±3.98	18.28±3.57	<0.001
6–13 years	17.88±3.55	18.30±3.75	17.44±3.25	<0.001
14–17 years	20.87±3.66	21.03±4.01	20.73±3.31	<0.001
Physical activity (PA, hour/day)
VPA	0.46±0.72	0.53±0.76	0.39±0.67	<0.001
6–13 years	0.46±0.67	0.51±0.71	0.41±0.61	<0.001
14–17 years	0.45±0.86	0.59±0.90	0.33±0.80	<0.001
MPA	0.46±0.71	0.50±0.75	0.42±0.66	<0.001
6–13 years	0.47±0.69	0.49±0.72	0.44±0.65	<0.001
14–17 years	0.43±0.77	0.52±0.84	0.36±0.70	<0.001
Walking	0.76±1.08	0.79±1.14	0.72±1.01	<0.001
6–13 years	0.73±1.05	0.76±1.11	0.70±0.98	<0.001
14–17 years	0.84±1.15	0.92±1.23	0.77±1.07	<0.001

BMI – body mass index; PA – physical activity; VPA – vigorous physical activity; MPA – moderate physical activity. P value presented as the difference between boys and girls.