Absolute Temperature Mean Changes and Emergency Department Visits for Asthma in Seoul, Korea: A Case-Crossover Study

Abstract

Background Although weather changes are known to cause asthma symptoms, there were not many studies how absolute daily temperature change affect on asthma and their impact on asthma-related health-care utilization is poorly understood. Aims The objective of the present study was to determine the associations between absolute temperature mean changes (ATMC) and asthma-related emergency department (ED) visits among all ages in Seoul, Korea in 2007-2010. Methods Descriptive analyses of patient and ED visit characteristics were performed. A case-crossover study utilizing time-stratified controls was conducted to determine the impact of ATMC which is absolute temperature change between the day of event and 1 to 7 days prior to the asthma ED visits. We defined ATMC07 as average of absolute daily mean temperature change between ED visit day through 7 days prior of the event. Multivariable conditional logistic regression demonstrated the relation between ED visits and ATMC after controlling for other weather, pollutant measures, and week of influenza. Results The case-crossover study showed a statistically significant relation between asthma-related ED visits and ATMC in winter while there was no significant relation with daily temperature and the rest of seasons. The results showed the effect size respectively after adjustment for daily mean air pressure, daily mean relative humidity, daily maximum of sulfur dioxide, nitrogen dioxide, and PM10 ; ATMC01 (odds ratio = 1.020, 95%CI 1.001-1.040), ATMC02 (odds ratio= 1.033, 95%CI 1.005-1.062), ATMC03, (odds ratio=1.041, 95%CI 1.008-1.075) , ATMC04 (odds ratio=1.051, 95%CI 1.012-1.091) , ATMC05 (odds ratio=1.060, 95%CI 1.017-1.105) , ATMC06 (odds ratio=1.052, 95%CI 1.007-1.098) , ATMC07 (odds ratio=1.048, 95%CI 1.000-1.098). Conclusions We found that the association between asthma-related ED visits and the absolute temperature mean change is significantly strong in winter and larger ATMC causes more frequent asthma-related ED visits.