title: Parkinson's disease and occupation: differences in associations by case identification method suggest referral bias.
abstract: METHODS
  We used a population-based sample of 403 Parkinson's disease cases and 405 controls to examine risks by occupation. Results were compared to a previous clinic-based analysis.
  
  
  RESULTS
  With censoring of jobs held within 10 years of diagnosis, the following had significantly or strongly increased risks: social science, law and library jobs (OR = 1.8); farming and horticulture jobs (OR = 2.0); gas station jobs (OR = 2.6); and welders (OR = 3.0). The following had significantly decreased risks: management and administration jobs (OR = 0.70); and other health care jobs (OR = 0.44).
  
  
  CONCLUSIONS
  These results were consistent with other findings for social science and farming occupations. Risks for teaching, medicine and health occupations were not elevated, unlike our previous clinic-based study. This underscores the value of population-based over clinic-based samples. Occupational studies may be particularly susceptible to referral bias because social networks may spread preferentially via jobs.
authors.affiliation: School of Population and Public Health, University of British Columbia, Vancouver, British Columbia, Canada.
authors.forename: Kay
authors.initials: K
authors.lastname: Teschke
authors.forename: Stephen A
authors.initials: SA
authors.lastname: Marion
authors.forename: Joseph K C
authors.initials: JK
authors.lastname: Tsui
authors.forename: Hui
authors.initials: H
authors.lastname: Shen
authors.forename: Kathrine
authors.initials: K
authors.lastname: Rugbjerg
authors.forename: M Anne
authors.initials: MA
authors.lastname: Harris
mesh_terms: D000288:Administrative Personnel / Q000706:statistics & numerical data; D000368:Aged; D000383:Agriculture / Q000706:statistics & numerical data; D000978:Antiparkinson Agents / Q000627:therapeutic use; D015982:Bias; D001955:British Columbia / Q000453:epidemiology; D016022:Case-Control Studies; D003132:Commerce / Q000706:statistics & numerical data; D011307:Drug Prescriptions / Q000706:statistics & numerical data; D004812:Epidemiologic Methods; D005260:Female; D005742:Gasoline; D006282:Health Personnel / Q000706:statistics & numerical data; D006801:Humans; D007407:Interviews as Topic; D007603:Jurisprudence; D007990:Libraries / Q000706:statistics & numerical data; D008297:Male; D008875:Middle Aged; D009784:Occupational Diseases / Q000188:drug therapy / Q000453:epidemiology*; D010300:Parkinson Disease / Q000188:drug therapy / Q000453:epidemiology*; D012017:Referral and Consultation / Q000706:statistics & numerical data*; D012942:Social Sciences / Q000706:statistics & numerical data; D013663:Teaching / Q000706:statistics & numerical data; D014896:Welding / Q000706:statistics & numerical data
chemical_list: D000978:Antiparkinson Agents; D005742:Gasoline
keywords: Parkinson's disease; occupational exposure; selection bias