title: Short-term changes in ambient particulate matter and risk of stroke: a systematic review and meta-analysis.
abstract: BACKGROUND
  Stroke is a leading cause of death and long-term disability in the United States. There is a well-documented association between ambient particulate matter air pollution (PM) and cardiovascular disease morbidity and mortality. Given the pathophysiologic mechanisms of these effects, short-term elevations in PM may also increase the risk of ischemic and/or hemorrhagic stroke morbidity and mortality, but the evidence has not been systematically reviewed.
  
  
  RESULTS
  We provide a comprehensive review of all observational human studies (January 1966 to January 2014) on the association between short-term changes in ambient PM levels and cerebrovascular events. We also performed meta-analyses to evaluate the evidence for an association between each PM size fraction (PM2.5, PM10, PM2.5-10) and each outcome (total cerebrovascular disease, ischemic stroke/transient ischemic attack, hemorrhagic stroke) separately for mortality and hospital admission. We used a random-effects model to estimate the summary percent change in relative risk of the outcome per 10-μg/m(3) increase in PM.
  
  
  CONCLUSIONS
  We found that PM2.5 and PM10 are associated with a 1.4% (95% CI 0.9% to 1.9%) and 0.5% (95% CI 0.3% to 0.7%) higher total cerebrovascular disease mortality, respectively, with evidence of inconsistent, nonsignificant associations for hospital admission for total cerebrovascular disease or ischemic or hemorrhagic stroke. Current limited evidence does not suggest an association between PM2.5-10 and cerebrovascular mortality or morbidity. We discuss the potential sources of variability in results across studies, highlight some observations, and identify gaps in literature and make recommendations for future studies.
authors.affiliation: Department of Epidemiology, Brown University School of Public Health, Providence, RI (Y.W., M.N.E., G.A.W.) Department of Environmental Health Sciences, Indiana University Fairbanks School of Public Health, Indianapolis, IN (Y.W.).
authors.forename: Yi
authors.initials: Y
authors.lastname: Wang
authors.affiliation: Department of Epidemiology, Brown University School of Public Health, Providence, RI (Y.W., M.N.E., G.A.W.).
authors.forename: Melissa N
authors.initials: MN
authors.lastname: Eliot
authors.affiliation: Department of Epidemiology, Brown University School of Public Health, Providence, RI (Y.W., M.N.E., G.A.W.).
authors.forename: Gregory A
authors.initials: GA
authors.lastname: Wellenius
mesh_terms: D020520:Brain Infarction / Q000150:complications / Q000453:epidemiology*; D002543:Cerebral Hemorrhage / Q000150:complications / Q000453:epidemiology*; D004781:Environmental Exposure / Q000706:statistics & numerical data*; D006801:Humans; D002546:Ischemic Attack, Transient / Q000453:epidemiology*; D052638:Particulate Matter; D020521:Stroke / Q000453:epidemiology* / Q000209:etiology
chemical_list: D052638:Particulate Matter
keywords: air pollution; cerebrovascular disease; meta‐analysis; particulate matter; stroke
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