title: Job demands and dementia risk among male twin pairs.
abstract: BACKGROUND
  Job characteristics may influence dementia risk, but some types of job complexity remain to be examined. Twin studies provide a useful methodology to examine job differences between pairs who share many environmental and genetic influences.
  
  
  METHODS
  Members of the NAS-NRC Twins Registry of World War II Veterans received a clinical evaluation for dementia and had job ratings from the Dictionary of Occupational Titles.
  
  
  RESULTS
  Cotwin-control models (n = 220 pairs) indicated lower dementia risk with greater job demands of reasoning, mathematics, language, and vocational training, with comparable results in case-control models (n=425 cases). These effects were significant among twin pairs discordant for 6 or more years, but not among those discordant between 3-5 years. Results were similar for Alzheimer's disease, and main effects were not further explained by zygosity or apolipoprotein E genotype.
  
  
  CONCLUSIONS
  Jobs that utilize data, academic skills, and extensive vocational training may protect against dementia; however, in twin pairs these effects only emerged among individuals who remained free of dementia several years after onset in their sibling.
authors.affiliation: Department of Psychiatry and Behavioral Sciences, Duke University Medical Center, Durham, NC, USA. guy.potter@duke.edu
authors.forename: Guy G
authors.initials: GG
authors.lastname: Potter
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Helms
authors.forename: James R
authors.initials: JR
authors.lastname: Burke
authors.forename: David C
authors.initials: DC
authors.lastname: Steffens
authors.forename: Brenda L
authors.initials: BL
authors.lastname: Plassman