Canadian Journal of Public Health

, Volume 105, Issue 5, pp e336–e341 | Cite as

Emergency department visits for asthma in relation to the Air Quality Health Index: A case-crossover study in Windsor, Canada

  • Mieczysław SzyszkowiczEmail author
  • Termeh Kousha
Quantitative Research


OBJECTIVES: In this study, associations of short-term changes in ambient air pollution with emergency department (ED) visits for asthma were examined in hospitals in the area of Windsor, Ontario. Ambient air pollution quality was represented by the Air Quality Health Index(AQHI), calculated using a formula that combines the concentrations and the relative health impacts of three ambient air pollutants: ozone, nitrogen dioxide and fine particulate matter.

METHODS: Data on ED visits were retrieved from the National Ambulatory Care Reporting System. Only patients two years of age and older were considered. A time-stratified case-crossover design was applied to 6,697 ED visits for asthma for the period of April 2004 to December 2010. Odds ratios (ORs) and their corresponding 95% confidence intervals (CIs) for ED visits associated with increased (by one unit) levels of AQHI were calculated by applying conditional logistic regression.

RESULTS: Positive and statistically significant results were observed between AQHI levels and ED visits for asthma. For all patients the largest value, OR=1.17 (CI: 1.09, 1.26), was obtained for exposures lagged by 9 days in the warm season (April-September). Effects among children 2 to 14 years of age were observed for same-day exposure (lag 0), with an OR=1.11(CI: 1.01, 1.21).

CONCLUSION: Exposure to ambient air pollution in Windsor increases the risk of ED visits for asthma. When the adverse effects of air pollutants are increased, patient visits to the ED depend on the patient’s age.


Air pollution air quality health index asthma emergency department 


OBJECTIFS: Dans cette étude, nous avons examiné les associations entre les changements à court terme dans la pollution atmosphérique et les visites aux urgences dues à l’asthme dans les hôpitaux de la région de Windsor (Ontario). La qualité de l’air ambiant a été représentée par la cote air santé (CAS), calculée selon une formule combinant les concentrations et les effets sanitaires relatifs de trois polluants atmosphériques: l’ozone, le dioxyde d’azote et les particules fines.

MÉTHODE: Les données sur les visites aux urgences ont été extraites du Système national d’information sur les soins ambulatoires. Seuls les patients âgés de deux ans et plus ont été pris en compte. Nous avons appliqué un schéma « case-crossover » stratifié dans le temps à 6 697 visites aux urgences dues à l’asthme pour la période d’avril 2004 à décembre 2010. Nous avons appliqué une régression logistique conditionnelle pour calculer les rapports de cotes (RC) et leurs intervalles de confiance (IC) à 95 % correspondants pour les visites aux urgences associées à des niveaux accrus (d’une unité) de la CAS.

RÉSULTATS: Des résultats positifs et significatifs ont été observés entre les niveaux de la CAS et les visites aux urgences dues à l’asthme. Pour l’ensemble des patients, la plus grande valeur, RC=1,17 (IC: 1,09, 1,26), a été obtenue pour les expositions décalées de 9 jours durant la saison chaude (avril-septembre). Des effets chez les enfants de 2 à 14 ans ont été observés pour les expositions le jour même (0 décalage), avec un RC=1,11 (IC: 1,01, 1,21).

CONCLUSION: L’exposition à la pollution atmosphérique à Windsor accroît le risque de visites aux urgences dues à l’asthme. Quand les effets indésirables des polluants atmosphériques augmentent, les visites aux urgences varient selon l’âge des patients.


pollution de l’air cote air santé asthme service urgences 


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Copyright information

© The Canadian Public Health Association 2014

Authors and Affiliations

  1. 1.Population Studies DivisionHealth CanadaOttawaCanada

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