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

Abstract

RATIONALE: 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. METHODS: 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. RESULTS: A smoothed plot suggested a dose-response association -as ambient grass pollen increased to about 19 grains/m 3 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). CONCLUSIONS: 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/m 3 , 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.

Do human rhinovirus infections and food allergy modify grass pollen–induced asthma hospital admissions in children?

“…1 Although the role of outdoor aeroallergens as triggers for asthma exacerbations requiring hospitalization in children and adolescents is complex, there is evidence that increasing concentrations of grass pollen are associated with an increased risk of asthma exacerbations in children. 2 Human rhinovirus (HRV) infections are implicated in most of the serious asthma exacerbations in school-age children. 3 In previous research, HRV infections and aeroallergen exposure have usually been studied independently.…”

“…However, in previous studies, the exposures to grass pollen were similar for residents across Melbourne. 2 In summary, boys with HRV infection at admission on days with high concentrations of outdoor grass pollen are at risk of asthma exacerbations requiring hospitalization. In contrast, girls sensitized to food were at an increased risk of admission on high pollen days.…”

Allergic rhinitis in children

“…19 In children with coexisting allergic rhinitis and asthma, exacerbation of allergic rhinitis leads to acute episodes of asthma, whereas treatment of rhinitis improves asthma control. 20 Children with allergic rhinitis are at a greater risk of asthma. 18 21 In a cohort study of 7383 children, allergic rhinitis in childhood was associated with a sevenfold increased risk of asthma in the preadolescent period.…”

Does allergy explain why some children have severe asthma?

“…34 In a study in Atlanta, ambient grass and tree pollen levels contributed to asthma morbidity in children, with a significant 10%-15% increase in emergency department attendances for asthma on the days with the highest pollen concentrations. 108 A recent meta-analysis showed small increases in grass pollen levels (of 10 grass pollen grains per cubic metre) are associated with a significant increase in mean number of asthma exacerbations in children presenting to the emergency department. 108 A recent meta-analysis showed small increases in grass pollen levels (of 10 grass pollen grains per cubic metre) are associated with a significant increase in mean number of asthma exacerbations in children presenting to the emergency department.…”