The Role of Seasonal Grass Pollen on Childhood Asthma Emergency Department Presentations

Abstract

Identifying high grass pollen days is important for asthma management programs that issue warnings to patients who are at an increased risk of an asthma attack due to grass pollen exposure. We sought to examine the association between increasing ambient concentrations of grass pollen and asthma Emergency Department (ED) presentations in children during the 2003 grass pollen season in Melbourne, Victoria; and whether there was any added influence from thunderstorms. A short time series ecological study was conducted of ED presentations for asthma in children in Melbourne, Victoria and grass pollen, meteorological and air quality measurements recorded during the selected 2003 period. A semi-parametric Poisson regression model was used to examine the dose-response associations between daily grass pollen levels and mean daily ED attendances for asthma among children. A smoothed plot suggested a dose-response association - as ambient grass pollen increased to about 19 grains/m3 the same day risk of childhood ED presentations also increased (p < 0.001). Grass pollen levels were also associated with an increased risk in asthma ED presentations on the following day (lag 1, p < 0.001). This is the first study to establish a clear relationship between increased risk of childhood asthma ED attendance and increasing levels of ambient grass pollen below 20 grains/m3, independent of thunderstorm-associated asthma. Lower levels of pollen may contribute to asthma symptoms, so the limits of the pollen season may need to be reviewed and this in turn could affect the timing of immunotherapy.