Table 1 Baseline characteristics of the study population [n(%)]
Variables | Total (n=18723) | Normal weight (n=12657) | Overweight (n=3711) | Obesity (n=2355) | P-value |
|---|---|---|---|---|---|
Age (years) | 12.6±3.1 | 12.5±4.2 | 12.9±3.2 | 13.1±3.5 | <0.001 |
Gender | Â | Â | Â | Â | <0.001 |
 Boys | 10191 | 6842 (67.1) | 1902 (18.7) | 1447 (14.2) |  |
 Girls | 8532 | 5815 (68.2) | 1809 (21.2) | 908 (10.6) |  |
Residence region | Â | Â | Â | Â | <0.001 |
 Urban | 13347 | 8484 (63.6) | 3122 (23.4) | 1741 (13.0) |  |
 Rural | 5376 | 4173 (77.6) | 589 (11.0) | 614 (11.4) |  |
Educational stages | Â | Â | Â | Â | <0.001 |
 Primary school | 7122 | 3488 (49.0) | 2492 (35.0) | 1142 (16.0) |  |
 Middle school | 5823 | 4590 (78.8) | 619 (10.6) | 614 (10.6) |  |
 High school | 5778 | 4579 (79.2) | 600 (10.4) | 599 (10.4) |  |
Height (cm) | 166.3±4.4 | 166.2±4.4 | 166.1±4.2 | 167.2±4.6 | <0.001 |
Weight (Kg) | 59.4±4.1 | 49.3±3.8 | 57.5±4.3 | 69.4±4.7 | 0.003 |
BMI (kg/m2) | 25.4±2.9 | 21.3±2.7 | 25.5±3.7 | 34.9±3.5 | <0.001 |
Paternal age | 41.2±2.0 | 41.1±2.0 | 41.2±3.7 | 41.0±2.0 | 0.001 |
Paternal BMI (kg/m2) | 26.5±2.7 | 20.9±1.8 | 25.1±3.2 | 32.5±1.7 | <0.001 |
Paternal education level | Â | Â | Â | Â | <0.001 |
 Middle school or below | 5220 | 3725 (71.4) | 812 (15.5) | 683 (13.1) |  |
 High school | 5159 | 3536 (68.6) | 986 (19.1) | 637 (12.3) |  |
 University or above | 8344 | 5396 (64.7) | 1913 (22.9) | 1035 (12.4) |  |
Maternal age | 40.0±3.0 | 40.1±3.0 | 39.7±3.0 | 40.3±3.1 | <0.001 |
Maternal BMI (kg/m2) | 25.8±1.9 | 21.1±1.1 | 25.2±2.9 | 31.6±2.3 | <0.001 |
Maternal education level | Â | Â | Â | Â | <0.001 |
 Middle school or below | 5589 | 4004 (71.6) | 866 (15.5) | 719 (12.9) |  |
 High school | 5222 | 3631 (69.5) | 987 (18.9) | 604 (11.6) |  |
 University or above | 7912 | 5022 (63.5) | 1858 (23.5) | 1032 (13.0) |  |
Sleep duration | Â | Â | Â | Â | <0.001 |
 Very short | 6560 | 4140 (63.1) | 1480 (22.6) | 940 (14.3) |  |
 Short | 5262 | 3636 (69.1) | 1017 (19.3) | 609 (11.6) |  |
 Recommended | 4529 | 3347 (73.9) | 742 (16.4) | 440 (9.7) |  |
 Long | 2372 | 1534 (64.7) | 472 (19.9) | 366 (15.4) |  |
Physical activity | Â | Â | Â | Â | <0.001 |
 ≤2h/day | 16044 | 10898 (67.9) | 2974 (18.6) | 2172 (13.5) |  |
 >2h/day | 2679 | 1759 (65.7) | 737 (27.5) | 183 (6.8) |  |
Internet surfing | Â | Â | Â | Â | 0.612 |
 ≤2h/day | 3399 | 2321 (68.3) | 664 (19.5) | 414 (12.2) |  |
 >2h/day | 15324 | 10336 (67.4) | 3047 (19.9) | 1941 (12.7) |  |
Watching TV | Â | Â | Â | Â | 0.079 |
 ≤2h/day | 5065 | 3488 (68.9) | 963 (19.0) | 614 (12.1) |  |
 >2h/day | 13658 | 9169 (67.1) | 2748 (20.1) | 1741 (12.8) |  |
Playing on phone | Â | Â | Â | Â | <0.001 |
 ≤2h/day | 1796 | 1114 (62.0) | 213 (11.9) | 469 (26.1) |  |
 >2h/day | 16927 | 11543 (68.2) | 3498 (20.7) | 1886 (11.1) |  |
Eating habits before sleeping | <0.001 | ||||
 Yes | 14827 | 10249 (69.1) | 2698 (18.2) | 1880 (12.7) |  |
 No | 3896 | 2408 (61.8) | 1013 (26.0) | 475 (12.2) |  |