Table 2.
Sample characteristics among boys and girls.
| Characteristics | Boys (n = 49,522) | Girls (n = 45,139) | p-value |
|---|---|---|---|
| Age (yrs) | 9.96 ± 2.47 | 9.98 ± 2.46 | 0.063 |
| Grade, n (%) | 0.058 | ||
| 1 | 14,288 (28.85) | 12,709 (28.15) | |
| 4 | 15,990 (32.29) | 14,752 (32.68) | |
| 7 | 19,244 (38.86) | 17,678 (39.16) | |
| Height (cm) | 138.37 ± 16.77 | 137.83 ± 15.96 | <0.001 |
| Weight (kg) | 37.18 ± 15.13 | 35.59 ± 13.42 | <0.001 |
| BMI | 18.64 ± 4.10 | 18.07 ± 3.70 | <0.001 |
| BMI group, n (%) | <0.001 | ||
| Underweight | 3,043 (6.14) | 2,988 (6.62) | |
| Normal | 31,755 (64.12) | 31305 (69.35) | |
| Overweight | 6,812 (13.75) | 5290 (11.72) | |
| Obese | 7,912 (15.98) | 5556 (12.31) | |
| Living area, n (%) | 0.017 | ||
| Industrial area | 31,365 (63.33) | 28,320 (62.74) | |
| Semi-industrial area | 3,211 (6.48) | 3,123 (6.92) | |
| Remote area | 14,950 (30.19) | 13,697 (30.34) | |
| Period, n (%) | 0.730 | ||
| 2009 | 5,714 (47.86) | 6,226 (52.14) | |
| 2010 | 5,266 (47.57) | 5,805 (52.43) | |
| 2011 | 4,938 (48.19) | 5,310 51.81) | |
| 2012 | 4,775 (47.37) | 5,306 (52.63) | |
| 2013 | 4,520 (47.71) | 4,953 (52.29) | |
| 2014 | 4,329 (48.30) | 4,633 (51.70) | |
| 2015 | 4,067 (46.88) | 4,608 (53.12) | |
| 2016 | 3,890 (47.56) | 4,289 (52.44) | |
| 2017 | 3,822 (48.03) | 4,136 (51.97) | |
| 2018 | 3,818 (47.29) | 4,256 (52.71) |