The association of asthma symptoms with specific skin-test sensitivity is well documented for many indoor allergens; however the importance of outdoor allergen exposures is less clearly understood. This study examines the hypothesis that the incidence of acute asthma attacks has a dose-dependent relationship with exposure to specific outdoor allergens.
Data on urgent care inhalation treatments and hospitalizations for asthma were collected from Jan 1999 through June 2004 from records of the Fallon Community Health maintenance organization which services Worcester, MA. Outdoor pollen and spores were measured with a Burkard sampler on the roof of the Worcester Medical Center. Taxonomic identifications were made microscopically to the lowest possible level. Pollen data from June 2001 - May 2004 and fungal spore data from June 2001 - September 2002 are used in this preliminary analysis.
A strong seasonal cycle in the prevalence of asthma attacks is evident with a slight peak period in the fall, and in summer approximately 50% fewer attacks than in winter and spring. While the general pattern is present across all age groups, it is most pronounced in school age children and least marked in those >55 years old. Asthma seasonality does not clearly match that of the aeroallergens. The most abundant pollen types are Quercus, Betula and Pinus while approximately 64% of total spore concentrations are hyaline basidiospores.
This preliminary analysis highlights the strong seasonality of both aeroallergens and asthma exacerbations as primary sources of variation to be accounted for in the Poisson time series modeling that will be the primary analytic tool for addressing this hypothesis.