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

Epidemiology. 2011 May;22(3):422-31. doi: 10.1097/EDE.0b013e3182126580.


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.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • 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


  • Particulate Matter