Characteristics of cases and controls
| Controls | Cases | |
| Subjects n# | 241 | 121 |
| Male % | 66.7 | 65.8 |
| Age yrs | 3.23 | 2.91 |
| Father's education yrs | 13.0 | 13.3 |
| Mother's education yrs | 14.2 | 14.1 |
| Parental asthma % | 9.1 | 20.7 |
| Current smoking at home % | 31.0 | 27.5 |
| Number of siblings % | ||
| 0 | 21.2 | 12.9 |
| 1 | 39.8 | 56.0 |
| 2+ | 38.8 | 31.1 |
| No day care <1 yr % | 98.3 | 95.0 |
| Child has lived on a farm % | 15.5 | 14.2 |
| Pets currently % | 48.3 | 28.1 |
| Building characteristics | ||
| Single family/row house % | 75.9 | 74.4 |
| Basement % | 17.5 | 11.8 |
| Timber/log frame % | 57.3 | 57.0 |
| Flat roof % | 14.9 | 8.3 |
| Renovated % | 79.2 | 79.0 |
| Natural ventilation % | 37.8 | 30.6 |
| Condensation on windows % | 33.7 | 40.4 |
| Use of humidifiers % | 7.5 | 12.7 |
| Use of additional heating % | 33.2 | 36.4 |
| Age of the building yrs | 24.8 | 26.7 |
| Size of the building m2 | 105.4 | 105.4 |
Data are presented as mean, unless otherwise stated. #: The number of observations with nonmissing data on different characteristics ranged 220–241 among controls and 116–121 among cases.