Table 1 General characteristics of the study participants
| Â | Total N=19,315 | Boys n=10,196 | Girls n=9119 |
|---|---|---|---|
Age, years | 13.0 (11.0, 16.0) | 13.0 (11.0, 16.0) | 14.0 (11.0, 16.0) |
9-10 | 3339 (17.3) | 1815 (17.8) | 1524 (16.7) |
11-12 | 4264 (22.1) | 2306 (22.6) | 1958 (21.5) |
13-14 | 4319 (22.4) | 2305 (22.6) | 2014 (22.1) |
15-16 | 4215 (21.8) | 2177 (21.4) | 2038 (22.3) |
17-18 | 3178 (16.5) | 1593 (15.6) | 1585 (17.4) |
Residence | Â | Â | Â |
Urban areas | 12,199 (63.2) | 6478 (63.5) | 5721 (62.7) |
Suburb areas | 7116 (36.8) | 3718 (36.5) | 3398 (37.3) |
Menarche | Â | Â | Â |
No | —— | —— | 2545 (27.9) |
Yes | —— | —— | 6574 (72.1) |
Age at menarche, years | —— | —— | 12.0 (11.0,13.0) |
Spermatorrhea | Â | Â | Â |
No | —— | 6437 (63.1) | —— |
Yes | —— | 3759 (36.9) | —— |
Age at first spermatorrhea, years | —— | 14.0 (13.0,14.0) | —— |
Height, cm | 160.0 (151.0, 168.0) | 165.5 (150.0, 173.0) | 158.0 (151.5, 163.0) |
Weight, kg | 51.0 (42.1, 60.4) | 54.4 (42.9, 65.4) | 48.8 (41.5, 55.4) |
BMI, kg/m2 | 19.7 (17.6, 22.3) | 20.0 (17.7, 23.0) | 19.3 (17.4, 21.6) |
Underweight | 994 (5.1) | 610 (6.0) | 384 (4.2) |
Normal weight | 12,964 (67.1) | 5998(58.8) | 6966 (76.4) |
Overweight | 3279 (17.0) | 2194 (21.5) | 1085 (11.9) |
Obesity | 2078 (10.8) | 1394 (13.7) | 684 (7.5) |
Sleep duration, h | Â | Â | Â |
≥ 8 | 9308 (48.2) | 5144 (50.5) | 4164 (45.7) |
< 8 | 10,007 (51.8) | 5052 (49.5) | 4955 (54.3) |
Sedentary time, h | Â | Â | Â |
< 8 | 15,946 (82.6) | 8666 (85.0) | 7280 (79.8) |
≥ 8 | 3369 (17.4) | 1530 (15.0) | 1839 (20.2) |
Frequency of exercise, times per week | Â | Â | Â |
≤ 1 | 4938 (25.6) | 2173 (21.3) | 2765 (30.3) |
2-4 | 8332 (43.1) | 4249 (41.7) | 4083 (44.8) |
≥ 5 | 6045 (31.3) | 3774 (37.0) | 2271 (24.9) |
Use of backpack posture | Â | Â | Â |
Double-shoulder bag | 16,401 (84.9) | 8698 (85.3) | 7703 (84.5) |
Single-shoulder bag | 2701 (14.0) | 1372 (13.5) | 1329 (14.6) |
Bag with wheels | 213 (1.1) | 126 (1.2) | 87 (1.0) |