title: Long-term exposure to air pollution and hospital admissions for ischemic stroke. A register-based case-control study using modelled NO(x) as exposure proxy.
abstract: BACKGROUND
  Long-term exposure to air pollution is a hypothesized risk factor for ischemic stroke. In a large case-control study with a complete study base, we investigated whether hospital admissions for ischemic stroke were associated with residential concentrations of outdoor NOx, as a proxy for exposure to air pollution, in the region of Scania, Southern Sweden.
  
  
  METHODS
  We used a two-phase case-control study design, including as first-phase controls all individuals born between 1923 and 1965 and residing in Scania in 2002 (N = 556 912). We defined first-phase cases as first-time ischemic stroke patients residing in Scania and registered in the Swedish stroke register between 2001 and 2005 (N = 4 904) and second-phase cases as cases for whom we had information on smoking status, diabetes, and medication for hypertension (N = 4 375). For the controls, information on these covariables was collected from a public health survey, resulting in 4 716 second-phase controls. With a geographical information system and an emission database, individual residential outdoor annual mean NOx concentration was modelled. The data were analyzed with logistic regression.
  
  
  RESULTS
  We found no evident association between NOx and ischemic stroke. For example, the odds ratio for ischemic stroke associated with the NOx category 20-30 microg/m3 compared to the reference category of <10 microg/m3 was 0.95 (95% CI 0.86-1.06).
  
  
  CONCLUSIONS
  In this study area, with generally low levels of air pollution, using a complete study base, high-quality ascertainment of cases, and individually modelled exposure, we did not observe any clear association between NOx and ischemic stroke hospital admissions.
authors.affiliation: Department of Occupational and Environmental Medicine, Lund University Hospital, Lund, Sweden. anna.oudin@med.lu.se
authors.forename: Anna
authors.initials: A
authors.lastname: Oudin
authors.forename: Emilie
authors.initials: E
authors.lastname: Stroh
authors.forename: Ulf
authors.initials: U
authors.lastname: Strömberg
authors.forename: Kristina
authors.initials: K
authors.lastname: Jakobsson
authors.forename: Jonas
authors.initials: J
authors.lastname: Björk
mesh_terms: D000368:Aged; D000393:Air Pollutants / Q000633:toxicity*; D002545:Brain Ischemia / Q000453:epidemiology* / Q000628:therapy; D016022:Case-Control Studies; D004781:Environmental Exposure; D006760:Hospitalization; D006801:Humans; D009569:Nitric Oxide / Q000633:toxicity*; D010343:Patient Admission; D012042:Registries; D020521:Stroke / Q000453:epidemiology* / Q000628:therapy; D013548:Sweden / Q000453:epidemiology
chemical_list: D000393:Air Pollutants; D009569:Nitric Oxide
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