Residential air pollution does not modify the positive association between physical activity and lung function in current smokers in the ECRHS study

Background: No study has yet examined whether any beneficial effect of physical activity on lung function can be influenced by living in polluted urban areas. Objective: We assessed whether annual average residential concentrations of nitrogen dioxide (NO2) and particulate matter with aerodynamic diameters <2.5µm (PM2.5) and <10µm (PM10) modify the effect of physical activity on lung function among never- (N=2801) and current (N=1719) smokers in the multi-center European Community Respiratory Health Survey. Methods: Associations between repeated assessments (at 27-57 and 39-67 years) of being physically active (physical activity: >2 times and >1 hour per week) and forced expiratory volume in one second (FEV1) and forced vital capacity (FVC) were evaluated using adjusted mixed linear regression models. Models were conducted separately for never- and current smokers and stratified by residential long-term NO2, PM2.5 mass and PM10 mass concentrations (< 75th percentile (low/medium) versus >75th percentile (high)). Results: Among never-smokers, physical activity was associated with lung function in areas with low/medium NO2 , PM2.5 mass and PM10 mass concentrations (e.g. mean difference in FVC between active and non-active subjects was 43.0mL (13.6, 72.5), 49.5mL (20.1, 78.8) and 49.7mL (18.6, 80.7), respectively), but these associations were attenuated in high air pollution areas. Among current smokers, physical activity and lung function were positively associated regardless of air pollution levels. Only the interaction term of physical activity and PM10 mass among never-smokers was significant for FEV1 (p-value=0.03). Conclusions: Physical activity has beneficial effects on adult lung function in current smokers,