European Journal of Epidemiology

, Volume 21, Issue 9, pp 689–700 | Cite as

Associations between outdoor air pollution and emergency department visits for stroke in Edmonton, Canada

  • Paul J. VilleneuveEmail author
  • Li Chen
  • Dave Stieb
  • Brian H. Rowe
Neurological Diseases


Inconsistent results have been obtained from studies that have examined the relationship between air pollution and hospital visits for stroke. We undertook a time-stratified case-crossover study to evaluate associations between outdoor air pollution and emergency department visits for stroke among the elderly according to stroke type, season, and sex. Analyses are based on a total of 12,422 stroke visits among those 65 years of age and older in Edmonton, Canada between April 1, 1992 and March 31, 2002. Daily air pollution levels for SO2, NO2, PM2.5, PM10, CO and O3 were estimated using data from fixed-site monitoring stations. Particulate matter data were only available from 1998 onwards. Conditional logistic regression was used to estimate the odds ratios (ORs) and their 95% confidence intervals in relation to an increase in the interquartile range (IQR) of each pollutant. ORs were adjusted for the effects of temperature and relative humidity. We found no association between outdoor measures of air pollution and all stroke visits. In contrast, elevated risks were observed between levels of air pollution and acute ischemic stroke between April and September. During this season, the ORs associated with an increase in the IQR of the 3-day average for CO and NO2 were 1.32 (95% CI = 1.09–1.60) and 1.26 (95% CI = 1.09–1.46), respectively. CO exposures in the same season, lagged 1 day, were associated with an increased risk of hemorrhagic stroke with ORs was 1.20 (95% CI = 1.00–1.43). Our results suggest it is possible that vehicular traffic, which produces increased levels of NO2 and CO, contributes to an increased incidence of emergency department visits for stroke.


Air pollution Case-crossover Ischemic stroke Risk Stroke 



Confidence interval


Emergency Department


International Classification of Diseases, 9th Revision


National Air Pollution Surveillance


Odds ratio


Transient ischemic attack


World Health Organization


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We acknowledge Environment Canada for providing the air pollution data from the National Air Pollution Surveillance (NAPS) network that was analyzed in this study. We appreciate the efforts of Ms. Chris Houston from Information Services, Capital Health for securing these data.


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Copyright information

© Springer Science+Business Media B.V. 2006

Authors and Affiliations

  • Paul J. Villeneuve
    • 1
    • 2
    Email author
  • Li Chen
    • 1
  • Dave Stieb
    • 1
  • Brian H. Rowe
    • 3
  1. 1.Air Health Effects DivisionEnvironmental Contaminants Bureau, Health CanadaOttawaCanada
  2. 2.Department of Public Health SciencesUniversity of TorontoTorontoCanada
  3. 3.Department of Emergency Medicine and Public Health Sciences, University of AlbertaAlbertaCanada

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