Does urban land-use increase risk of asthma symptoms?

Global urbanization is increasing rapidly, especially in Asian countries. The health impacts of this unprecedented rate of urbanization are not well understood. Prevalence of asthma is also increasing, especially in cities.

We explored the effects of urbanicity, based on urban land-use and traffic-related air pollutants (NO2, PM10), on asthma symptoms and diagnosis at a nationally representative level, using individual-level data from the 2008-2010 Community Health Survey data in Korea. We applied logistic regression, adjusting for sex, age, education, smoking status, and household income. To investigate whether different levels of urban intensity (i.e., degree of urbanization) affected the association, we stratified analysis by urban intensity for the subject's residential district: high (≥30% urban), medium (10-30%), and low intensity (<10%).

Increased urban land-use was significantly associated with increased risk of asthma symptoms and diagnosis. A 10% increase of urban land-use of a subject's residential district was associated with an odds ratio (OR) of 1.03 (95% CI: 1.02, 1.04) for self-reported physician-diagnosed asthma. However, increased urbanicity is associated with higher risk of asthma in areas with a baseline of low urbanicity, but not in areas with a baseline of high urbanicity. Significant positive associations were also observed for air pollution (PM10 and NO2) with asthma symptoms and diagnosis.

Our findings suggest that increases in urbanicity or air pollution are associated with increased risk of asthma, and that the level of urban intensity affected the associations.