title: Is outdoor work associated with elevated rates of cerebrovascular disease mortality? A cohort study based on iron-ore mining.
abstract: BACKGROUND
  A cohort study that examined iron ore mining found negative associations between cumulative working time employed underground and several outcomes, including mortality of cerebrovascular diseases. In this cohort study, and using the same group of miners, we examined whether work in an outdoor environment could explain elevated cerebrovascular disease rates.
  
  
  METHODS
  This study was based on a Swedish iron ore mining cohort consisting of 13,000 workers. Poisson regression models were used to generate smoothed estimates of standardized mortality ratios and adjusted rate ratios, both models by cumulative exposure time in outdoor work.
  
  
  RESULTS
  The adjusted rate ratio between employment classified as outdoor work ≥25 years and outdoor work 0-4 years was 1.62 (95 % CI 1.07-2.42). The subgroup underground work ≥15 years deviated most in occurrence of cerebrovascular disease mortality compared with the external reference population: SMR (0.70 (95 % CI 0.56-0.85)).
  
  
  CONCLUSIONS
  Employment in outdoor environments was associated with elevated rates of cerebrovascular disease mortality. In contrast, work in tempered underground employment was associated with a protecting effect.
authors: Department of Radiation Sciences (Oncology), Umeå University, SE-901 85 Umeå, Sweden.
authors: Ove
authors: 0000-0002-6080-5973
authors: O
authors: Björ
authors: Department of Radiation Sciences (Oncology), Umeå University, SE-901 85 Umeå, Sweden.
authors: Håkan
authors: H
authors: Jonsson
authors: Department of Radiation Sciences (Oncology), Umeå University, SE-901 85 Umeå, Sweden.
authors: Lena
authors: L
authors: Damber
authors: Department of Public Health & Clinical Medicine, Occupational and Environmental Medicine, Umeå University, SE-901 85 Umeå, Sweden.
authors: Lage
authors: L
authors: Burström
authors: Department of Public Health & Clinical Medicine, Occupational and Environmental Medicine, Umeå University, SE-901 85 Umeå, Sweden.
authors: Tohr
authors: T
authors: Nilsson
keywords: Cohort study; Mining; Mortality; Occupation; Poisson regression; Standardized mortality ratio