title: Influence of outdoor aeroallergens on hospitalization for asthma in Canada.
abstract: BACKGROUND
  The risk of hospitalization for asthma caused by outdoor aeroallergens is largely unknown.
  
  
  OBJECTIVE
  The objective of this study was to determine the association between changes in outdoor aeroallergens and hospitalizations for asthma from the Pacific coast to the Atlantic coast of Canada.
  
  
  METHODS
  A daily time series analysis was done to test the association between daily changes in aeroallergens and daily changes in hospitalizations for asthma during a 7-year period between 1993 and 2000 in 10 of the largest cities in Canada. Results were adjusted for long-term trends, day of the week, climate, and air pollution.
  
  
  RESULTS
  A daily increase, equivalent to the mean value of each allergen, was associated with the following percentage increase in asthma hospitalizations: 3.3% (95% CI, 2.3 to 4.1) for basidiomycetes, 3.1% (95% CI, 2.8 to 5.7) for ascomycetes, 3.2% (95% CI, 1.6 to 4.8) for deuteromycetes, 3.0% (95% CI, 1.1 to 4.9) for weeds, 2.9% (95% CI, 0.9 to 5.0) for trees, and 2.0% (95% CI, 1.1 to 2.8) for grasses. After accounting for the independent effects of trees and ozone, the combination of the 2 was associated with an additional 0.22% increase in admissions averaged across cities (P <.05).
  
  
  CONCLUSIONS
  These findings provide evidence for the hypothesis that aeroallergens are an important cause of severe asthma morbidity across Canada, and in some situations there might be a modest synergistic adverse effect of ozone and aeroallergens combined.
authors.affiliation: University of Ottawa, Ottawa, Ontario, Canada.
authors.forename: Robert E
authors.initials: RE
authors.lastname: Dales
authors.forename: Sabit
authors.initials: S
authors.lastname: Cakmak
authors.forename: Stan
authors.initials: S
authors.lastname: Judek
authors.forename: Tom
authors.initials: T
authors.lastname: Dann
authors.forename: Frances
authors.initials: F
authors.lastname: Coates
authors.forename: Jeffrey R
authors.initials: JR
authors.lastname: Brook
authors.forename: Richard T
authors.initials: RT
authors.lastname: Burnett
mesh_terms: D000293:Adolescent; D000328:Adult; D000393:Air Pollutants / Q000032:analysis*; D000485:Allergens / Q000009:adverse effects / Q000032:analysis*; D001249:Asthma / Q000453:epidemiology* / Q000209:etiology; D002170:Canada / Q000453:epidemiology; D002648:Child; D002675:Child, Preschool; D006760:Hospitalization / Q000639:trends*; D006801:Humans; D006109:Poaceae / Q000009:adverse effects; D011058:Pollen / Q000009:adverse effects*; D012621:Seasons; D013172:Spores, Fungal / Q000302:isolation & purification*; D014197:Trees / Q000009:adverse effects
chemical_list: D000393:Air Pollutants; D000485:Allergens