Table 1.
Characteristics of the study population and the variables of interest.
| Variable | n/N (%) or Mean ± SD (N) |
|---|---|
| Socio-demographic | |
| Age (years) | 10.0 ± 1.2 (2872) |
| Female | 1466/2872 (51) |
| Index of relative socioeconomic advantage and disadvantage IRSAD |
1022 ± 76 (2872) |
| Maternal education—tertiary; | 1730/2788 (62) |
| secondary | 932/2788 (33.5) |
| Day care attendance in first year of life | 690/2825 (24.4) |
| Number of siblings—more than one; | 569/2822 (20.2) |
| one | 1016/2822 (36.0) |
| Atopic Illnesses | |
| Maternal atopic diseases | 1628/2872 (56.7) |
| Children with asthma | 781/2840 (27.5) |
| Children with eczema | 645/2794 (23.1) |
| Children with any positive skin prick test | 989/2078 (47.6) |
| Indoor Exposures | |
| Gas for cooking—first year of life | 1732/2774 (62.4) |
| Gas for cooking—current | 1904/2840 (67.0) |
| Gas for heating—first year | 936/2872 (32.6) |
| Gas for heating—current | 945/2872 (32.9) |
| Wood stove or open fire—first year | 470/2872 (16.4) |
| Wood stove or open fire—current | 393/2872 (13.7) |
| Heating reverse cycle air conditioning—first year | 340/2872 (11.8) |
| Heating reverse cycle air conditioning—current | 917/2872 (31.9) |
| Pet ownership (cat or dog) | 2140/2830 (75.6) |
| Maternal smoking—first year | 566/2728 (20.8) |
| Maternal smoking—current | 546/2820 (19.4) |
| Smoking in house—current | 260/2854 (9.1) |
| Air Pollution | |
| Lifetime NO2 average exposure (parts per billion) | 9.3 +/− 3.3 (2847) |
| Outcome | |
| Otitis media (lifetime) | 1097/2783 (39.4) |