title: Employment as a welder and Parkinson disease among heavy equipment manufacturing workers.
abstract: OBJECTIVE
  We investigated whether employment as a welder with potential exposure to manganese and other substances is associated with Parkinson disease (PD), parkinsonism or related neurological disorders, or accelerates the age of onset of PD.
  
  
  METHODS
  We selected cases and controls from 12,595 persons ever employed at three Caterpillar Inc. (CAT) plants between 1976 and 2004 with potential to make a medical insurance claim between 1998 and 2004. Cases had filed a claim for 1) PD, 2) "secondary parkinsonism", 3) "other degenerative diseases of the basal ganglia" or 4) "essential and other specific forms of tremor". Cases were grouped by claims: Group 1-claims 1 and 2 and Group 2-claims 1 to 4, and as study period incident (SPI) or prevalent. Each case was matched to two series of 10 controls each on date of case's first claim, year of birth, race and sex. Series I was also matched on plant.
  
  
  RESULTS
  Odds ratios (OR) and 95% confidence intervals (CI) for the variable, "ever welder in any CAT plant" were: Group 1-SPI Cases: Series I (OR = .76, CI = .26-2.19), Series II (OR = .81, CI = .29-2.25); Group 1- Prevalent Cases: Series I (OR = .82, CI = .36-1.86), Series II (OR = .97, CI = .42-2.23); Group 2- SPI Cases: Series I (OR = 1.03, CI = .57-1.87), Series II (OR = 1.21, CI = .67-2.20) Group 2-Prevalent Cases: Series I (OR = 1.02, CI = .62-1.71), Series II (OR = .86, CI = .51-1.43). Our finding of no statistically significant associations for welding employment was maintained following adjustment for potential confounding and evaluation of possible effect modification. Employment as a welder did not accelerate the age of onset of PD.
  
  
  CONCLUSIONS
  Our study supported the conclusion that employment as a welder is not associated with Parkinson disease, parkinsonism or a related neurological disorder.
authors.affiliation: Department of Biostatistics, Graduate School of Public Health, University of Pittsburgh, Pittsburgh, Pennsylvania 15261, USA. gmarsh@pitt.edu
authors.forename: Gary M
authors.initials: GM
authors.lastname: Marsh
authors.forename: Mary Jean
authors.initials: MJ
authors.lastname: Gula
mesh_terms: D000328:Adult; D016022:Case-Control Studies; D015331:Cohort Studies; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D007087:Illinois / Q000453:epidemiology; D008297:Male; D008345:Manganese / Q000009:adverse effects; D008875:Middle Aged; D009784:Occupational Diseases / Q000453:epidemiology*; D016273:Occupational Exposure / Q000009:adverse effects*; D016017:Odds Ratio; D010300:Parkinson Disease / Q000453:epidemiology* / Q000209:etiology; D013232:Steel / Q000009:adverse effects; D014896:Welding
chemical_list: D013232:Steel; D008345:Manganese