Social and demographic characteristics
| Variable | No respiratory symptom | Respiratory disease | p‐value |
| Subjects | 2016 | 407 | |
| Age yrs | 9.79±2.29 | 10.11±2.38 | 0.02 |
| 5–7 | 307 (18.2) | 54 (16.8) | 0.50 |
| 8–9 | 491 (29.1) | 84 (26.1) | |
| 10–11 | 589 (34.9) | 118 (36.6) | |
| 12–16 | 303 (17.9) | 66 (20.5) | |
| Sex | |||
| M | 1147 (57.1) | 248 (61.7) | 0.09 |
| F | 861 (42.9) | 154 (38.3) | |
| BMI | 18.25±8.22 | 19.12±9.14 | 0.04 |
| Home smokers | 1.21±0.93 | 1.46±1.06 | <0.001 |
| Pet raising | 280 (13.9) | 84 (20.6) | <0.001 |
| Playing with dust | 476 (23.6) | 153 (37.6) | <0.001 |
| Allergy | 136 (6.7) | 114 (28.0) | <0.001 |
| Father's education | |||
| <8 yrs school | 1073 (56.4) | 223 (59.2) | 0.56 |
| >8 yrs school | 747 (39.2) | 140 (37.1) | |
| University | 84 (4.4) | 14 (3.7) | |
| Mother's education | |||
| <8 yrs school | 994 (51.9) | 216 (56.1) | 0.31 |
| >8 yrs school | 849 (44.3) | 155 (40.3) | |
| University | 74 (3.9) | 14 (3.6) | |
| Father lung disease | 204 (10.1) | 73 (17.9) | <0.001 |
| Mother lung disease | 169 (8.4) | 70 (17.2) | <0.001 |
Data are presented mean±sd or as n (%)
M: male
F: female
BMI: body mass index