Effect of traffic proximity of lung function in asthmatic children

Introduction Respiratory conditions are strongly dependent on air pollution. Urban areas are typically characterized by risky environmental conditions, especially due to traffic congestion. Indeed, there may be important variations in environmental quality even within urban areas. Objectives To analyze the effect of traffic proximity on asthma and to explore the relationship between level of traffic proximity and lung function in both asthmatic children and non-asthmatic children. Methods A case-control study on children visited for suspected respiratory diseases at IBIM from September 2011 to May 2014 was performed. All the children have been geocoded according to their residence address. After geocoding, level of exposure to environmental conditions was assessed through determination of number and types of streets in proximity of the place of residence. High traffic roads (HTR) were defined as all roads segments with at least 10,000 vehicles per- day. Moreover, the city area has been divided in two main polygons: city centre, North area and suburbs. Their relationship with lung function was explored jointly with other variables collected through questionnaire surveys and laboratory functional tests. As for the lung function, spirometric indices (FEV1; FVC; FEV1/FVC; FEF25-75) were obtained by using a portable spirometer (Pony FX, Cosmed, Italy) and they were expressed as percent predicted using GLI-2012 equation. A measure of restrictive pattern was determined as the ratio FEV1/FVC > LLN and FVC <LLN, by using GLI. Results There were 386 children, 90 (23.3%) of which with diagnosis of persistent asthma, 105 (27.2%) with diagnosis of intermittent asthma, and 191 (49.5%) composed by those who have been visited at IBIM during the study period, but did not resulted in an asthma diagnosis (i.e. controls). Level of exposure to traffic conditions, did not showed significant differences between cases (persistent and intermittent asthmatics) and controls, neither at a distance of 100 meters from the place of residence, nor at 200 and 500 meters. Associations between environmental conditions and lung function were analyzed, among those subjects for which spirometric measures were available (n=341). FEV1 index expressed as a percentage of predicted was used to classify children lung function in two categories, i.e. above and below 95% (Table 1). Association between living in proximity to HTR and worst lung function resulted only for children with persistent asthma (OR=4,02; CI= 1,47; 10,97). Indeed, further analyses on lung function indices such as FEV1/FVC<LLN; did not resulted associated with traffic proximity measures. Conclusion Our preliminary results do not show differences in environmental conditions as measured through traffic proximity indices among persistent asthmatics, intermittent asthmatics and controls. However, association between lung function and traffic proximity is observed for asthmatic children. These results, if confirmed, would indicate that living in proximity to HTR, although not being a risk factor for asthma can be a determinant for worst lung functions among asthmatic subjects.