Air pollution, socioeconomic position, and emergency hospital visits for asthma in Seoul, Korea

  • Sun-Young Kim
  • Marie S. O’Neill
  • Jong-Tae Lee
  • Youngtae Cho
  • Jaiyong Kim
  • Ho Kim
Original Article



Some epidemiological literature has observed that air pollution effects on health differed across regional or individual socioeconomic position. This study evaluated whether regional and individual socioeconomic position, as indicated by health insurance premiums, modified the effect of air pollution on hospital visits for asthma.


Effects of ambient air pollutants (particulate matter, carbon monoxide, sulfur dioxide, nitrogen dioxide, and ozone) on 92,535 emergency out-patient hospital visits for asthma in Seoul, Korea during 2002 were estimated using case-crossover analysis, adjusting for time trend, weather conditions, and seasonality. Next, interactions between air pollutants and Korean National Health Insurance premium (1) for the individual patient and (2) averaged across the patient’s residence district, were entered, first singly then jointly, in the models.


Relative risks of emergency outpatient hospital visits were all positively and significantly associated with interquartile increases for selected lags for all air pollutants. In the regression model with interaction terms for both individual premium and regional-average premium, associations with all five-air pollutants ranged from 1.03 to 1.09 times higher among the lowest premium districts compared to the highest premium districts. Of all the pollutants, nitrogen dioxide showed the strongest associations in lower premium districts compared to the higher premium districts. Individual socioeconomic position did not modify the associations in either the single or joint interaction models.


In Seoul, community but not individual socioeconomic conditions modified risk of asthma hospital visits on high air pollution days.


Air pollution Asthma Effect modifier Residence characteristics Socioeconomic factors 



Confidence interval


Carbon monoxide


Korean National Health Insurance


Nitrogen dioxide


Particulate matter ≤10 μm in aerodynamic diameter


Relative effect modification


Relative risk


Socioeconomic position


Sulfur dioxide


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Copyright information

© Springer-Verlag 2007

Authors and Affiliations

  • Sun-Young Kim
    • 1
  • Marie S. O’Neill
    • 2
  • Jong-Tae Lee
    • 3
  • Youngtae Cho
    • 4
  • Jaiyong Kim
    • 5
  • Ho Kim
    • 4
  1. 1.Department of Environment and Occupational Health Sciences, School of Public Health and Community MedicineUniversity of WashingtonSeattleUSA
  2. 2.Departments of Epidemiology and Environmental Health Sciences, School of Public HealthUniversity of MichiganAnn ArborUSA
  3. 3.Department of Health Management, Graduate SchoolHanyang UniversitySeoulSouth Korea
  4. 4.Department of Epidemiology and Biostatistics, Graduate School of Public Health and The Institute of Health and EnvironmentSeoul National UniversitySeoulSouth Korea
  5. 5.Primary Health Care Team, Research DepartmentKorea Health Insurance Review AgencySeoulSouth Korea

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