Table 1 Characteristics of the study population
|  | Total (N = 2639) | Female (n = 1218) | Male (n = 1421) | P value |
|---|---|---|---|---|
Age (years) | 13.18 ± 0.93 | 13.12 ± 0.90 | 13.22 ± 0.95 | 0.005 |
Grade | Â | Â | Â | 0.769 |
 Grade 7 | 1005 (38.1) | 472 (38.8) | 533 (37.5) |  |
 Grade 8 | 727 (27.5) | 335 (27.5) | 392 (27.6) |  |
 Grade 9 | 907 (34.4) | 411 (33.7) | 496 (34.9) |  |
Height, cm | 164.52 ± 8.51 | 161.25 ± 6.39 | 167.32 ± 9.08 | < 0.001 |
Weight, kg | 55.32 ± 11.64 | 52.01 ± 9.31 | 58.16 ± 12.65 | < 0.001 |
BMI, kg/m2 | 20.35 ± 3.48 | 19.96 ± 3.15 | 20.68 ± 3.70 | < 0.001 |
SBP, mmHg | 108.08 ± 12.41 | 104.71 ± 11.08 | 110.97 ± 12.75 | < 0.001 |
DBP, mmHg | 65.64 ± 8.35 | 65.45 ± 8.04 | 65.80 ± 8.60 | 0.277 |
Sleep quality | Â | Â | Â | 0.487 |
 Good | 2121 (80.4) | 986 (81.0) | 1135 (79.9) |  |
 Pool | 518 (19.6) | 232 (19.0) | 286 (20.1) |  |
Smartphone addiction | Â | Â | Â | 0.586 |
 Negative | 2037 (77.2) | 946 (77.7) | 1091 (76.8) |  |
 Positive | 602 (22.8) | 272 (22.3) | 330 (23.2) |  |