Prolonged Effect of Air Pollution on Pneumonia: a Nationwide Cohort Study
Introduction: Although acute exposure to ambient air pollution is a possible risk factor for pneumonia, little is known about the effect of prolonged exposure.
Aims and Objectives: This study aims to investigate whether prolonged exposure to air pollutants is associated with pneumonia.
Methods: We calculated the incidence rates of pneumonia using a nationwide sample cohort which comprised one million random subjects from the Korean National Health Insurance Sharing Service. Daily levels of nitrogen oxide (NO2), sulfur dioxide (SO2), particulate matter (PM10), ozone (O3) and carbon monoxide (CO) were obtained from the Korean Ministry of Environment, and matched in each of the sixteen administrative district regions of Korea. We employed a Poisson regression analysis for regional results, and a meta-analysis with random effect model for showing the overall associations. We examined the lag effect up to 10 weeks preceding the occurrence of pneumonia.
Results: We detected 76,508 cases of pneumonia from 2011 to 2013. Annual incidence rates of pneumonia were 2.44 to 2.62 person per one million. NO2 and SO2 concentrations had a significant association with incidence of pneumonia at time lag 0 (10.13±2.34, p<0.001 for NO2, 25.98±9.68, p=0.04 for SO2), extending back to 5 weeks for NO2 (2.42±0.72, p=0.003) and 10 weeks for SO2 (5.71±1.87, p=0.01). The association of PM10 and pneumonia was inconsistent at different time points, and even O3 levels showed negative correlation with pneumonia. We found no significant correlation with CO.
Conclusions: Exposure to NO2 and SO2 was associated with an increased incidence of pneumonia in Korea. Moreover, the effect of air pollution exposure lasted up to 5 weeks for NO2 and 10 weeks for SO2.