Background: The interrelationships between air pollution, lung function and childhood asthma incidence has yet to be established. Hypothesis: To determine whether lung function is associated with new onset asthma and whether this relationship varies by exposure to ambient air pollutants.
Methods: A cohort of fourth grade children who were asthma- and wheeze- free at study entry were identified from the Children's Health Study and followed for eight years. The participants resided in 12 communities with a wide range of ambient air pollutants that were measured continuously. Spirometry was performed and medical diagnosis of asthma was ascertained annually. Proportional hazard regression models were fitted to investigate the relationship of lung function (FVC, FEV1, and FEF25-75) at study entry with subsequent development of asthma and to determine whether air pollutants modify these associations.
Results: We found levels of airway flow was associated with new onset asthma. Over the 10th-90th percentile range of FEF25-75 (57.1%), the hazard ratio (HR) of new onset asthma was 0.50 (95% CI: 0.35-0.71). This protective effect of better lung function was reduced in children exposed to higher levels of PM2.5. Over the 10th-90th percentile range of FEF25-75, the HR of new onset asthma was 0.34 (0.21-0.56) in communities with low PM2.5 (<13.7 μgm/m3) and 0.76 (0.45-1.26) in communities with high PM2.5 (≥13.7μgm/m3). A similar pattern was observed for FEV1. Little variation in HR was observed for O3.
Conclusion: Exposure to high levels of PM2.5 attenuates the protective effect of better lung function against new onset asthma.
- Air pollution
- Cohort study
- Lung fucntion