Table 3. Initial characteristics of the study subjects followed or not-followed for 3 years.
| Characteristics | Follow-up (n = 1,858) (%) |
No follow-up (n = 648) (%) |
p-value |
| Sex | |||
| Male | 51.2 | 48.1 | 0.183 |
| Female | 48.8 | 51.9 | |
| Asthma | 6.6 | 8.3 | 0.143 |
| Wheeze | 5.2 | 6.0 | 0.440 |
| History of allergic diseases | 54.6 | 49.7 | 0.030 |
| Respiratory diseases before 2 years of age | 10.7 | 10.3 | 0.792 |
| Breast feeding in infancy | 27.7 | 34.4 | 0.001 |
| Parental history of allergic diseases | 45.3 | 44.8 | 0.822 |
| Maternal smoking habits | 10.8 | 14.0 | 0.025 |
| House of steel or reinforced concrete | 31.1 | 42.9 | < 0.001 |
| Use of unvented heater in winter | 63.1 | 67.0 | 0.075 |
| Areas | |||
| Urban areas | |||
| 0-49 m from trunk roads | 6.7 | 7.9 | 0.002 |
| ≥ 50 m from trunk roads | 48.2 | 55.1 | |
| Rural areas | 45.1 | 37.0 |