title: Omega-3 fatty acids and risk of dementia: the Canadian Study of Health and Aging.
abstract: BACKGROUND
  Omega-3 polyunsaturated fatty acids (n-3 PUFAs) may protect against dementia, although epidemiologic studies have yielded inconclusive results. Fish is the main dietary source of n-3 PUFAs and is sometimes contaminated with mercury. This neurotoxicant may modify the association with dementia.
  
  
  OBJECTIVE
  We evaluated the association of erythrocyte membrane total n-3 PUFAs, docosahexaenoic acid (DHA), eicosapentaenoic acid (EPA), and blood mercury with the incidence of dementia and Alzheimer disease (AD) in the Canadian Study of Health and Aging (CSHA) with adjustment for confounders including apolipoprotein E epsilon4 (APOE epsilon4) status.
  
  
  METHODS
  The CSHA is a cohort study of a representative sample of persons aged > or =65 y, conducted from 1991 to 2002. A subsample of 663 nondemented CSHA subjects with a complete clinical examination, blood samples, and follow-up information was eligible for prospective analyses on laboratory measurements. Of these, 149 were incident cases of dementia, including 105 with AD.
  
  
  RESULTS
  In adjusted Cox regression models with age as the time scale, there were no associations between total n-3 PUFAs, DHA, or EPA and dementia or AD. In contrast, a mercury concentration in the highest quartile was associated with a reduced risk of dementia (hazard ratio: 0.53; 95% CI: 0.33, 0.88). However, significant risk reductions were limited to subjects with concentrations of both n-3 PUFAs and mercury that were above the median. There was no modification of risk by APOE epsilon4 status.
  
  
  CONCLUSIONS
  No associations between n-3 PUFAs and dementia or AD were found. The results regarding mercury may indicate a spurious association.
authors.affiliation: Centre d'Excellence sur le Vieillissement de Quebec, Unite de Recherche sur le Vieillissement, Centre de Recherche FRSQ du Centre Hospitalier Affilie Universitaire de Québec, Québec, Canada.
authors.forename: Edeltraut
authors.initials: E
authors.lastname: Kröger
authors.forename: René
authors.initials: R
authors.lastname: Verreault
authors.forename: Pierre-Hugues
authors.initials: PH
authors.lastname: Carmichael
authors.forename: Joan
authors.initials: J
authors.lastname: Lindsay
authors.forename: Pierre
authors.initials: P
authors.lastname: Julien
authors.forename: Eric
authors.initials: E
authors.lastname: Dewailly
authors.forename: Pierre
authors.initials: P
authors.lastname: Ayotte
authors.forename: Danielle
authors.initials: D
authors.lastname: Laurin
mesh_terms: D000368:Aged; D000375:Aging; D000544:Alzheimer Disease / Q000453:epidemiology* / Q000517:prevention & control; D053327:Apolipoprotein E4 / Q000627:therapeutic use; D002170:Canada / Q000453:epidemiology; D015331:Cohort Studies; D004281:Docosahexaenoic Acids / Q000097:blood; D015118:Eicosapentaenoic Acid / Q000097:blood; D015525:Fatty Acids, Omega-3 / Q000097:blood* / Q000627:therapeutic use*; D006801:Humans; D008137:Longitudinal Studies; D008628:Mercury / Q000097:blood*; D012044:Regression Analysis
chemical_list: D053327:Apolipoprotein E4; D015525:Fatty Acids, Omega-3; D004281:Docosahexaenoic Acids; D015118:Eicosapentaenoic Acid; D008628:Mercury