The results of studies examining the relationship of domestic factors to lung function are contradictory. We therefore examined the independent effects of maternal smoking during pregnancy, exposure to environmental tobacco smoke (ETS), the presence of a cat, type of heating and cooking used in the home and day-care attendance on lung function after controlling for socioeconomic status (SES). Nine hundred and eighty-nine children from 18 Montreal schools were studied between April 1990 and November 1992. Information on the child's health and exposure to domestic factors was collected by questionnaire. Spirometry was performed at school. The data were analysed by multiple linear regression with percent predicted FEV1, FVC, and as dependent variables. In the overall sample (both sexes combined), cat in the home (regression coefficient, β = −1·15, 95% confidence interval, CI: −2·26–−0·05) and electric baseboard units (β = −1·26, 95% CI: −2·39–−0·13) were independently associated with a lower , while day-care attendance (β = −2·05, 95% CI: −3·71–−0·40) significantly reduced FEV1. Household ETS was significantly associated with increasing level of FVC (β = 2·86, 95% CI: +0·55 to +5·17). In boys but not girls, household ETS (β = −2·13, 95% CI: −4·07–−0·19) and the presence of a cat (β = −2·19, 95% CI: −3·94–−0·45) were associated with lower . By contrast, day-care attendance was associated with lower FEV1 (β = −2·92, 95% CI: −5·27–−0·56) and (β = −1·53, 95% CI: −2·73–−0·33) in girls only. In conclusion, the results provide evidence that domestic factors and day-care attendance primarily affected airway caliber and gender differences were apparent in the effects of these factors.
