title: Fine particulate air pollution (PM2.5) and the risk of acute ischemic stroke.
abstract: BACKGROUND
  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.
  
  
  METHODS
  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.
  
  
  RESULTS
  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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: National University of Ireland, Galway, Ireland. odonnm@mcmaster.ca
authors.forename: Martin J
authors.initials: MJ
authors.lastname: O'Donnell
authors.forename: Jiming
authors.initials: J
authors.lastname: Fang
authors.forename: Murray A
authors.initials: MA
authors.lastname: Mittleman
authors.forename: Moira K
authors.initials: MK
authors.lastname: Kapral
authors.forename: Gregory A
authors.initials: GA
authors.lastname: Wellenius
mesh_terms: D000208:Acute Disease; D017677:Age Distribution; D000368:Aged; D000369:Aged, 80 and over; D002545:Brain Ischemia / Q000139:chemically induced / Q000453:epidemiology; D015331:Cohort Studies; D016001:Confidence Intervals; D004781:Environmental Exposure / Q000009:adverse effects*; D005260:Female; D006801:Humans; D002546:Ischemic Attack, Transient / Q000139:chemically induced / Q000453:epidemiology; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D016017:Odds Ratio; D009864:Ontario / Q000453:epidemiology; D052638:Particulate Matter / Q000009:adverse effects*; D011379:Prognosis; D012042:Registries; D018570:Risk Assessment; D017678:Sex Distribution; D020521:Stroke / Q000139:chemically induced* / Q000453:epidemiology*; D015996:Survival Rate; D014505:Urban Population
chemical_list: D052638:Particulate Matter