title: Outdoor work and risk for Parkinson's disease: a population-based case-control study.
abstract: OBJECTIVE
  Sunlight is the main contributor to vitamin D in humans. Since inadequate levels of vitamin D have been linked to increased risks for neurodegenerative diseases, we examined whether outdoor work is associated with a reduced risk for Parkinson's disease in a population-based case-control study of Danish men.
  
  
  METHODS
  We identified 3819 men with a primary diagnosis of Parkinson's disease in the period 1995-2006 in the Danish National Hospital Register and selected 19,282 age- and sex-matched population controls at random from the Central Population Register. Information on work history was ascertained from the Danish Supplementary Pension Fund and the Central Population Register. Based on trade grouping codes and job titles, we evaluated the extent of outdoor work of study subjects as a proxy of exposure to sunlight.
  
  
  RESULTS
  Relying on trade grouping codes, we estimated ORs for study subjects with moderate, frequent and maximal outdoor work compared with exclusive indoor work of 0.90 (95% CI 0.78 to 1.02), 0.86 (95% CI 0.75 to 0.99) and 0.72 (95% CI 0.63 to 0.82), respectively, for Parkinson's disease. Reduced risks were also found for Parkinson's disease among outdoor workers based on study subjects' job titles.
  
  
  CONCLUSIONS
  Our findings suggest that men working outdoors have a lower risk for Parkinson's disease. Further studies of measured vitamin D levels in outdoor workers are warranted to clarify a potential inverse association between vitamin D and the risk for Parkinson's disease.
authors.affiliation: Institute of Cancer Epidemiology, Danish Cancer Society, Strandboulevarden 49, 2100 Copenhagen, Denmark. kenborg@cancer.dk
authors.forename: Line
authors.initials: L
authors.lastname: Kenborg
authors.forename: Christina F
authors.initials: CF
authors.lastname: Lassen
authors.forename: Beate
authors.initials: B
authors.lastname: Ritz
authors.forename: Eva S
authors.initials: ES
authors.lastname: Schernhammer
authors.forename: Johnni
authors.initials: J
authors.lastname: Hansen
authors.forename: Nicole M
authors.initials: NM
authors.lastname: Gatto
authors.forename: Jørgen H
authors.initials: JH
authors.lastname: Olsen
mesh_terms: D000328:Adult; D017677:Age Distribution; D000368:Aged; D000369:Aged, 80 and over; D003718:Denmark / Q000453:epidemiology; D004812:Epidemiologic Methods; D006801:Humans; D008048:Lip Neoplasms / Q000453:epidemiology; D008175:Lung Neoplasms / Q000453:epidemiology; D008297:Male; D008875:Middle Aged; D016273:Occupational Exposure / Q000032:analysis*; D009790:Occupations / Q000706:statistics & numerical data; D010300:Parkinson Disease / Q000453:epidemiology* / Q000517:prevention & control; D012923:Social Class; D013472:Sunlight