Effect of indoor air quality in the postnatal period on lung function in pre-adolescent children: a retrospective cohort study in Poland.

The purpose of this study was to determine the association between level of lung function in pre-adolescence and indoor air quality in the postnatal period. The retrospective cohort study was carried out in a sample of 1036 pre-adolescent children (9 years of age) attending schools in two residential areas of Krakow, Poland. Measurement of health outcomes considered lung function together with height and weight. Indoor air quality was based on environmental tobacco smoke and type of household heating. In addition, the number of winter months that occurred during the first 6 months of life was included as a key independent variable. Multivariate linear regression of lung function measured by forced expiratory volume in 1s (FEV1) and forced vital capacity (FVC), and postnatal exposure to indoor pollution in the heating season (PEIP score) was adjusted for potential confounders such as maternal smoking during pregnancy and parental education as a proxy of social class. In the total study sample, the adjusted beta coefficient for FEV1 per unit of the PEIP score was -0.06 (P=0.02), while that for FVC was -0.05 (P=0.04). The analysis carried out in the more polluted area found that children living in households heated with gas or coal had a PEIP score that was strongly inversely related to lung function (adjusted beta coefficient for FEV1=-0.13; P=0.03; for FVC=-0.15, P=0.01), whereas regression coefficients were not significant in the group of children living in households with central heating. This study suggests that a lower level of lung function in pre-adolescent children can be related to postnatal exposure to indoor emissions in the winter.