Short-term Atmospheric Environmental Changes and Exacerbations on Respiratory Symptoms Using Emergency Department Visit Data in Seoul

Abstract

Background: Asthma and chronic obstructive pulmonary disease (COPD) are significant public health burdens. Atmospheric factors such as sunlight, temperature, and precipitation influence the ambient concentrations of air pollutants, leading to seasonal and diurnal changes in respiratory symptoms. Although the control of environmental factors such as meteorological variables and air pollutant variables is not in the scope of ability that the individuals is capable to control, the individuals is able to change their behavior and pattern of life against unfavorable environments and this may contribute on less exposure and less spending on medical expenditures. Thus, understanding the relationship between atmospheric environmental changes and exacerbations on the respiratory disease are necessary. Methods: I evaluated emergency department (ED) visits in Seoul, Korea between 2007 and 2011 to investigate the relationship between respiratory health outcome and short-term atmospheric environmental changes. I examined respiratory-related ED visits for asthma and COPD. Demographic factors such as age, sex, and socio-economic status (SES) and season were examined as effect modifiers. I applied generalized linear models (GLM) and case-crossover design for quantifying the estimated effect of environmental changes on ED visits. In order to explore the association between the exacerbations of respiratory symptoms and short-term environmental changes, various approach in the environmental exposures were examined. In the first instance, I examined the relationship with outdoor temperature changes during several consecutive days (TC) and secondly, hourly differences on the level of air pollutants, and the size fractions of particulate matters (PM10, PM10-2.5, and PM2.5) on asthma exacerbation. The time resolution of hourly differences was stratified as 1?6, 7?12, 13?18, 19?24, 25?48, and 48?72 hours on case and controls. Finally, I examined the health effect of nitrogen dioxide (NO2) and its diurnal range as a traffic-related pollutant in metropolitan area. In the overall analysis model, mean temperature, relative humidity, air pressure, various pollutants (PM10, PM10-2.5, PM2.5, O3, and NO2), day of the week, and influenza were adjusted and the adjustment of rainfall, and seasonal and long-term trends were applied if necessary. Results: In the study on asthma exacerbations by temperature variables, TC was adversely associated with asthma-related ED visits, with a 1-unit increase of temperature change associated with a [3.5% (95% CI 0.7, 6.4%)] increase in asthma- related ED visits. In addition, seasonal variation after adjusting for mean temperature and diurnal temperature range (DTR) were found with an adverse effect in spring, summer, and fall and a protective effect in winter. Patients aged ≥65 years experienced the most prominent effect during the fall, with a 17.9% (95% CI 4.1, 33.6%) increase in ED visits per 1-unit increase of temperature change, whereas the other seasons showed no statistically significant association. In the study for hourly differences on asthma exacerbations and the level of air pollutants, the highest adverse effect [OR, (95% CI)] was of PM10-2.5 after 1?6 h [1.05, (1.00, 1.11)], and of O3, after 19?24 h [1.10, (1.04, 1.16)]. Among the four seasons, highest effect of PM10-2.5 was in spring at 1-6 h lag [1.14, (1.06, 1.22)], while that of O3 in winter at 25?48 h lag [1.25, (1.03, 1.51)]. Effect of ozone was age-modified, and more immediate and greater in low SES patients at 7?12 h lag [1.25 (1.04, 1.51)] than high SES patients. In the study on traffic-related air pollutants and respiratory disease, NO2 and diurnal range of NO2 (drNO2) suggested increased risk of respiratory-related ED visits and, season and age-specific effect. The overall estimated relative risk percent change with 95% confidence interval (95% CI), at lag 0-7, by the 1 IQR increase of NO2 were [6.9 % (95 % CI -0.1 %, 14.4 %)], [13.1 % (95 % CI 4.1 %, 22.9 %)], and [1.7 % (95 % CI -6.7 %, 10.9 %)] for lower respiratory-, COPD-, and asthma-related ED visits respectively. During summer, asthma-related ED visits was increased by the level of NO2 [47.5 % (95 % CI 19.2 %, 82.6 %)] and age-specific modification was detected that lower respiratory- and COPD-related ED visits among aged <19, 20-49, and 50-74. Age-specific effect was observed for the increase of drNO2 specifically for the elderly ≥75 [52.5 % (95 % CI 3.8 %, 123.9 %)] during summer. Conclusions: Atmospheric short-term environmental changes were found to be a predictor of ED visits for asthma and COPD, and this relationship was modified by season and demographic factors. The study demonstrate that asthma-related ED visits increased along with an increase of TC and DTR. And increased PM10-2.5 and O3 levels lead to increased risk of asthma exacerbation and lower respiratory-related ED visits increased along with an increase of traffic-related pollutants not only the level but the diurnal variation of the pollutant. The findings indicate that public intervention in metropolitan area should focus on the vulnerable populations who has asthma and COPD as underlying disease among the children and the elderly who the adaption to outdoor environmental changes could take much longer time.