title: Hospital admissions for ischemic stroke: does long-term exposure to air pollution interact with major risk factors?
abstract: BACKGROUND
  The aim was to investigate whether the effects of major risk factors for ischemic stroke were modified by long-term exposure to air pollution in Scania, southern Sweden.
  
  
  METHODS
  Cases were defined as first-ever ischemic strokes in patients born between 1923 and 1965 during 2001-2006 (n = 7,244). Data were collected from The Swedish National Stroke Register (Riks-stroke) and the Malmö and Lund Stroke Registers. Population controls were matched on age and sex. Modeled outdoor annual mean NO(x) concentrations were used as proxy for long-term exposure to air pollution. Heterogeneity across NO(x) categories was tested for smoking, hypertension, diabetes mellitus, atrial fibrillation and physical inactivity. Data were analyzed as case-control data and to some extent as case-only data, with logistic regression analysis.
  
  
  RESULTS
  The case-control odds ratios for ischemic stroke in association with diabetes were 1.3 [95% confidence interval (CI): 1.1-1.6] and 2.0 (95% CI: 1.2-3.4) in the lowest and highest NO(x) category, respectively (p value for testing heterogeneity across the categories = 0.056). The case-only approach gave further support for the risk associated with diabetes to increase with NO(x) (p for trend = 0.033). We observed no main effect of mean NO(x) or any conclusive effect modifications between NO(x) and smoking, hypertension, atrial fibrillation or physical inactivity.
  
  
  CONCLUSIONS
  In a low-level air pollution area, the risk for ischemic stroke associated with diabetes seemed to increase with long-term exposure to air pollution.
authors.affiliation: Division of Occupational and Environmental Medicine, Umeå University, Umeå, Sweden. anna.oudin@med.lu.se
authors.forename: Anna
authors.initials: A
authors.lastname: Oudin
authors.forename: Ulf
authors.initials: U
authors.lastname: Strömberg
authors.forename: Kristina
authors.initials: K
authors.lastname: Jakobsson
authors.forename: Emilie
authors.initials: E
authors.lastname: Stroh
authors.forename: Arne G
authors.initials: AG
authors.lastname: Lindgren
authors.forename: Bo
authors.initials: B
authors.lastname: Norrving
authors.forename: Hélène
authors.initials: H
authors.lastname: Pessah-Rasmussen
authors.forename: Gunnar
authors.initials: G
authors.lastname: Engström
authors.forename: Jonas
authors.initials: J
authors.lastname: Björk
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000393:Air Pollutants / Q000009:adverse effects*; D002545:Brain Ischemia / Q000209:etiology*; D016022:Case-Control Studies; D048909:Diabetes Complications / Q000209:etiology; D004781:Environmental Exposure; D006801:Humans; D016015:Logistic Models; D008875:Middle Aged; D009589:Nitrogen Oxides / Q000009:adverse effects*; D016017:Odds Ratio; D010343:Patient Admission / Q000706:statistics & numerical data; D012042:Registries; D018570:Risk Assessment; D012307:Risk Factors; D020521:Stroke / Q000209:etiology*; D013548:Sweden
chemical_list: D000393:Air Pollutants; D009589:Nitrogen Oxides