Abstract
In epidemiological studies that examine associations between air pollution and aggravation of asthma is information on airborne pollen not always incorporated, ignoring their role and potential bias. Our aim was to study the short-term effects of two major types of allergenic pollen in Sweden, birch and grass, on daily emergency department visits for asthma (ICD10: J45-J46), in the three largest cities in Sweden (Stockholm, Gothenburg and Malmö). Focus was on daily total visits and visits in separate age classes (children and adults). Data from 2001 through 2008 were collected. To study the effect of pollen at different pollen concentrations, pollens were categorized into concentration intervals defined on the basis of the standard scale for forecast of daily pollen levels. We used additive Poisson regression models. Lag 01 of birch and grass pollen and air pollution variables (PM10, O3 and NOx) were simultaneously included in the model. We found that the birch pollen was positively associated with emergency department visits for asthma in Stockholm. For example, we estimated the increase of 3 % (95% CI 2.5 to 3.5%) in daily visits for all ages and 2 % (95% CI 1.5 to 2.9 %) among children per 100 grains/m3 increase in highest interval (> 100 grains/m3), respectively. In Gothenburg we found a tendency for birch pollen to be positively associated with asthma visits among children and grass pollen among adults, respectively. In Malmö, no statistically significant effects of any studied pollen on daily visits for asthma were found. There seem to be regional differences in effects of different types of pollen. The representativity of pollen measurements may be one explanation.
- © 2014 ERS