A prospective study of the association between home gas appliance use during infancy and subsequent dust mite sensitization and lung function in childhood

Background: Home gas appliance use has been associated with child respiratory illness but prospective data on the relationship between infant exposure and the development of child allergic disease has not been readily available. Objectives: (a) To determine if home gas appliance use is associated with increased risk of house dust mite (HDM) sensitization. (b) To examine whether any association between current home gas use and airway obstruction is influenced by HDM sensitization. Methods: Design: an 8-year follow-up birth cohort study of children born during 1988 and 1989. Participants: a population-based sample (n=498) of children who participated in the Tasmanian Infant Health Survey (TIHS) and resided in Northern Tasmania in 1997 (84% of eligible children). Main outcome measures: (a) Skin prick test reaction to nine allergens, including Dermatophagoides pteronyssinus (Der p 1) and Dermatophagoides farinae (Der f 1). (b) Spirometric lung function indices, including forced expiratory volume in one second (FEV1) and forced vital capacity (FVC). Results: The relative risk for home gas appliance use at 1 month of age and HDM sensitization was 1.98 (1.04, 3.79) in a cohort analysis with confounder matching. Current home gas use was also associated with HDM sensitization (ARR 1.73 (1.43, 2.76)). Current home gas use was related to a stronger (P=0.006) reduction in the FEV1: FVC ratio among HDM-sensitive children (adjusted difference -6.2% (-10.0 to-2.4)) than non-HDM-sensitive children (adjusted difference -0.3% (-2.5 to 1.8)). Conclusion: Indoor pollutants from gas combustion may increase the likelihood of initial sensitization to HDM and play a role in the development of atopic asthma. HDM-sensitized children may be more vulnerable to indoor pollutant-induced airway obstruction. The ability of this study to detect such effects may partly reflect unflued gas appliance use among this sample.