Childhood social position and associations between environmental exposures and health outcomes.

Background: Growing evidence indicates that environmental exposures are more prevalent among socially disadvantaged groups. We investigated the distribution of environmental exposures and health outcomes in preschool children, and examined the role of social position on their associations.

Methods: We analysed data from a cross-sectional study on 968 preschool children from three districts in the Ruhr Area and one rural community in North Rhine-Westphalia in 2000. Parents filled in a questionnaire on socio-demographic characteristics, environmental exposures, respiratory infections and allergic diseases. Residential annual total suspended particulate matter (TSP) mass concentrations were derived from a small-scale interpolation model. Lung function, allergic sensitisation and immunologic function were assessed. We analysed the associations between environmental exposures and health outcomes in social subgroups with logistic regression.

Results: High TSP concentrations at the home address and unfavourable living conditions were more prevalent in the socially disadvantaged groups, while allergic and respiratory infectious diseases were reported more frequently in the privileged groups. The odds ratio for the association between TSP and history of allergic diseases was 1.17 (95% CI 0.95-1.45) in children without immigration background and 0.71 (95% CI 0.53-0.95) with immigration background. Heterogeneity for exposure-outcome associations was also seen between TSP and lung function as well as unfavourable living conditions and allergic diseases.

Conclusions: We found evidence for an influence of social position on environment-health associations. Possible explanations for heterogeneity include social group-specific over- and underreporting and effect measure modification, which need to be taken into account when designing and analysing environmental health studies.