Ambient Air Pollution and Daily Emergency Department Visits for Ischemic Stroke in Edmonton, Canada

In this report, we examine the associations between emergency department (ED) visits for acute ischemic stroke and environmental conditions.The study concerned 10,881 ED visits for acute ischemic stroke (ICD-9: 434, 436) recorded at Edmonton hospitals between 1992 and 2002. Generalized linear mixed models technique was applied to build the statistical models. The logarithm of daily counts of ED visits for stroke was regressed on the levels of air pollutants (CO, NO2, SO2, and O3) and two meteorological variables. The analyses were performed by (a) age: two age groups were distinguished: 20-64 years (n=2873) and 65-100 years (n=8008); (b) season (all seasons: January-December, warm: April-September, cold: October-March); and (c) gender (both, male, female).The results are reported as an excess risk in relation to an increase in the interquartile range (IQR) of the pollutants. In the age group 65-100 years, the excess risk for particular pollutants was as follows: for NO2-8.2% (95% CI: 0.4-16.7) for both genders, in the warm season; for SO2-9.1% (95% CI: 2.2-16.4), for males, in the warm season: for a 1-day lagged SO2-6.0% (95% CI: 0.5-11.8), for females, in the cold season. Among the patients aged 20-64 years, the excess risk for NO2 was 6.3% (95% CI: 0.2-12.8), for both genders, and all seasons; and 13.8% (95% CI: 2.1-26.7), for females, in the cold season; for a 1-day lagged O3-17.8% (95% CI: 2.2-35.6), for males, in the warm season; for a 1-day lagged SO2-10.3% (95% CI: 0.7-20.9) for females, in the cold season.The findings provide evidence that exposure to air pollutants is significantly associated with ED visits for acute ischemic stroke.