Table 1.
Demographic characteristics of the study participants
| Characteristics | n | % |
| Respiratory symptoms | ||
| No | 3098 | 86.7 |
| Yes | 477 | 13.3 |
| SHS exposure in general | ||
| No | 1101 | 30.8 |
| Yes | 2474 | 69.2 |
| SHS exposure in indoor public places | ||
| No | 1806 | 50.5 |
| Yes | 1769 | 49.5 |
| SHS exposure in homes | ||
| No | 2342 | 65.5 |
| Yes | 1233 | 34.5 |
| SHS exposure in indoor campuses | ||
| No | 2763 | 77.3 |
| Yes | 812 | 22.7 |
| SHS exposure in outdoor campuses | ||
| No | 2532 | 70.8 |
| Yes | 1043 | 29.2 |
| Asthma history | ||
| No | 3514 | 98.3 |
| Yes | 61 | 1.7 |
| Grade | ||
| 1–2 | 2329 | 65.2 |
| 4–5 | 1246 | 34.8 |
| Only child | ||
| No | 1353 | 37.8 |
| Yes | 2222 | 62.2 |
| Gender | ||
| Male | 1818 | 50.9 |
| Female | 1757 | 49.1 |
| Pocket money monthly(¥) | ||
| <100 | 2039 | 57.0 |
| 100-399 | 1125 | 31.5 |
| ≥400 | 411 | 11.5 |
| Father’s education | ||
| Primary school | 838 | 23.4 |
| Middle school | 1215 | 34.0 |
| University and above | 1522 | 42.6 |
| Mother’s education | ||
| Primary school | 978 | 27.4 |
| Middle school | 1165 | 32.6 |
| University and above | 1432 | 40.0 |
%, the proportion of participants.; n, number of participants.
SHS, second-hand smoke.