Fine particulate air pollution (PM2.5) and the risk of acute ischemic stroke

• Published in: Epidemiology (Cambridge, Mass.) Vol. 22; no. 3; p. 422
• Main Authors: O'Donnell, Martin J, Fang, Jiming, Mittleman, Murray A, Kapral, Moira K, Wellenius, Gregory A
• Format: Journal Article
• Language: English
• Published: United States 01.05.2011
• Subjects: Acute Disease; Age Distribution; Aged; Aged, 80 and over; Brain Ischemia - chemically induced; Brain Ischemia - epidemiology; Cohort Studies; Confidence Intervals; Environmental Exposure - adverse effects; Female; Humans; Ischemic Attack, Transient - chemically induced; Ischemic Attack, Transient - epidemiology; Logistic Models; Male; Middle Aged; Odds Ratio; Ontario - epidemiology; Particulate Matter - adverse effects; Prognosis; Registries; Risk Assessment; Sex Distribution; Stroke - chemically induced; Stroke - epidemiology; Survival Rate; Urban Population; Ontario
• ISSN: 1531-5487
• DOI: 10.1097/EDE.0b013e3182126580

Short-term changes in levels of fine ambient particulate matter (PM2.5) may increase the risk of acute ischemic stroke; however, results from prior studies have been inconsistent. We examined this hypothesis using data from a multicenter prospective stroke registry. We analyzed data from 9202 patients hospitalized with acute ischemic stroke, having a documented date and time of stroke onset, and residing within 50 km of a PM2.5 monitor in 8 cities in Ontario, Canada. We evaluated the risk of ischemic stroke onset associated with PM2.5 in each city using a time-stratified case-crossover design, matching on day of week and time of day. We then combined these city-specific estimates using random-effects meta-analysis techniques. We examined whether the effects of PM2.5 differed across strata defined by patient characteristics and ischemic stroke etiology. Overall, PM2.5 was associated with a -0.7% change in ischemic stroke risk per 10-μg/m increase in PM2.5 (95% confidence interval = -6.3% to 5.1%). These overall negative results were robust to a number of sensitivity analyses. Among patients with diabetes mellitus, PM2.5 was associated with an 11% increase in ischemic stroke risk (1% to 22%). The association between PM2.5 and ischemic stroke risk varied according to stroke etiology, with the strongest associations observed for strokes due to large-artery atherosclerosis and small-vessel occlusion. These results do not support the hypothesis that short-term increases in PM2.5 levels are associated with ischemic stroke risk overall. However, specific patient subgroups may be at increased risk of particulate-related ischemic strokes.