Emergency Department Visits for Asthma Exacerbation due to Weather Conditions and Air Pollution in Chuncheon, Korea: A Case-Crossover Analysis

Abstract

PurposeThis retrospective study was conducted to estimate the effects of climate factors and air pollution on asthma exacerbations using a case-crossover analysis.MethodsPatients who visited the emergency department (ED) of 2 university hospitals in Chuncheon for asthma exacerbations from January 1, 2006, to December 31, 2011, were enrolled. Daily average data for meteorological factors (temperature, daily temperature range, relative humidity, wind speed, atmospheric pressure, presence of rain, solar irradiation, and presence of fog) and the daily average levels of gaseous air pollutants (SO2, NO2, O3, CO, and PM10) were obtained. A case-crossover analysis was performed using variables about the weather and air pollution at 1-week intervals between cases and controls before and after ED visits.ResultsThere were 660 ED visits by 583 patients with asthma exacerbations. Low relative humidity (lag 1 and 2) and high wind speed (lag 1, 2, and 3) were associated with ED visits for asthma. Fog (lag 2) showed protective effects against asthma exacerbations in Chuncheon (risk increase: -29.4% [95% CI=-46.3% to -7.2%], P=0.013). These relationships were stronger in patients ≤19 years old than in those >60 years old. High levels of ambient CO (lag 1, 2, and 3) and NO2 (lag 2 and 3) were associated with decreased ED visits for asthma. However, there were no significant relationships among levels of ambient CO or NO2 and asthma exacerbations after adjusting for wind speed and relative humidity.ConclusionsHigh wind speed and low humidity were associated with an increased risk of asthma ED visits. Fog was associated with a decreased risk of asthma ED visits after controlling for seasonal variations in weather and air pollution.

Relationship between biometeorological factors and the number of hospitalizations due to asthma

“…Some researchers notice a significant increase in asthma exacerbation cases under the weather conditions characterized by higher ambient air humidity, and link this fact to higher counts of fungal spores [61][62][63] . Kwon et al associated this phenomenon with the occurrence of fog, which often accompanies higher air humidity, and which alone -by being acid aerosol -is yet another air pollutant 64 . Others emphasize an increase in hospital admissions due to asthma on days with lower air humidity 65 .…”

Regular follow-up visits reduce the risk for asthma exacerbation requiring admission in Korean adults with asthma

“…Second, we could not analyze the potential variables that affect the frequency of visits and prognosis due to the retrospective nature of this study. For instance, adherence to medication, the dose of the inhaler, socio-economic status, clinical characteristics, residential district, and weather may be influential factors [ 26 , 27 ]. In this retrospective study, which used claim data from a national medical insurance review system, the available variables were extremely restricted.…”

Short-term effects of multiple outdoor environmental factors on risk of asthma exacerbations: Age-stratified time-series analysis

“…It is uncertain whether the effect of humidity on AEs is direct or indirect (because humidity is related to aeroallergen and air pollutant levels). 24 Several studies showed that AE events were directly associated with high humidity, 11,13,25 but another study showed that AE events were associated with low humidity. 26 Our results showed that humidity had a significant effect on AEs in the single model but not in the final model.…”