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JPMPH : Journal of Preventive Medicine and Public Health

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2 "Case-crossover studies"
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Original Article
Associations between Air Pollution and Asthma-related Hospital Admissions in Children in Seoul, Korea: A Case-crossover Study.
Jong Tae Lee
Korean J Prev Med. 2003;36(1):47-53.
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  • 56 Download
AbstractAbstract PDF
OBJECTIVES
I used a case-crossover design to investigate the association between air pollution, and hospital admissions for asthmatic children under the age of 15 years in Seoul, Korea METHODS: I estimated the changes in the levels of hospitalization risk from theinterquartile (IQR) increase in each pollutant concentrations, using conditional logistic regression analyses, with controls for weather information. RESULTS: Using bidirectional control sampling, the results from a conditional logistic regression model, with controls for weather conditions, showed the estimated relative risk of hospitalization for asthma among children to be 1.04 (95% confidence interval (CI), 1.01-1.08) for particulate matter with an aerodynamic diameter less than or equal to 10m (IQR=40.4ug/m3) ; 1.05 (95% CI, 1.00-1.09) for nitrogen dioxide (IQR=14.6ppb) ; 1.02 (95% CI, 0.97-1.06) for sulfur dioxide (IQR=4.4ppb) ; 1.03 (95% CI, 0.99-1.08) for ozone (IQR=21.7ppb) ; and 1.03 (95% CI, 0.99-1.08) for carbon monoxide (IQR=1.0ppm). CONCLUSIONS: This empirical analysis indicates the bidirectional control sampling methods, by design, would successfully control the confounding factors due to the long-term time trends of air pollution. These findings also support the hypothesis that air pollution, at levels below the current ambient air quality standards of Korea, is harmful to sensitive subjects, such as asthmatic children.
Summary
English Abstract
Effects of Air Pollution on Asthma in Seoul: Comparisons across Subject Characteristic.
Sun Young Kim, Ho Kim, Jaiyong Kim
J Prev Med Public Health. 2006;39(4):309-316.
  • 2,385 View
  • 60 Download
AbstractAbstract PDF
OBJECTIVES
Korean epidemiological studies have used reduced samples according to the subject's characteristics, such as the health services provided, the historical note with asthma, and age, to examine the acute effect of air pollution on asthma using the Korean National Health Insurance records. However, there have been few studies on whether the effects shown in these reduced samples are different from those of all samples. This study compared the effects of air pollution on asthma attacks in three reduced samples with those of entire samples. METHODS: The air pollution data for PM10, CO, SO2, NO2, and O3 and weather conditions including temperature, relative humidity, and air pressure in Seoul, 2002, were obtained from outdoor monitoring stations in Seoul. The emergency hospital visits with an asthma attack in Seoul, 2002 were extracted from the Korean National Health Insurance records. From these, the reduced samples were created by health service, historical notes with asthma, and age. A case-crossover design was adopted and the acute effects of air pollution on asthma were estimated after adjusting for weather, time trend, and seasonality. The model was applied to each reduced sample and the entire sample. RESULTS: With respect to the health service, the effects on outpatients were similar to those for the total sample but were different for inpatients. These similar effect sizes were also observed in the reduced samples according to the historical note with asthma and age. The relative risks of PM10, CO, SO2, NO2, and O3 among the reduced and entire samples were 1.03, 1.04-1.05, 1.02-1.03, 1.04-1.06, and 1.10-1.17, respectively. CONCLUSIONS: There was no clear evidence to show a difference between the reduced samples and the entire samples.
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JPMPH : Journal of Preventive Medicine and Public Health