Omega-3 fatty acids and risk of dementia: the Canadian Study of Health and Aging.
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.
Kröger
Edeltraut
E
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.
Verreault
René
R
Carmichael
Pierre-Hugues
PH
Lindsay
Joan
J
Julien
Pierre
P
Dewailly
Eric
E
Ayotte
Pierre
P
Laurin
Danielle
D
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
D053327:Apolipoprotein E4; D015525:Fatty Acids, Omega-3; D004281:Docosahexaenoic Acids; D015118:Eicosapentaenoic Acid; D008628:Mercury