Omega-3 fatty acids and risk of dementia: the Canadian Study of Health and Aging

• Published in: The American journal of clinical nutrition 2009-07, Vol.90 (1), p.184-192
• Main Authors: Kröger, Edeltraut, Verreault, René, Carmichael, Pierre-Hugues, Lindsay, Joan, Julien, Pierre, Dewailly, Éric, Ayotte, Pierre, Laurin, Danielle
• Format: Article
• Language: English
• Subjects: Aged; Aging; Alzheimer disease; Alzheimer Disease - epidemiology; Alzheimer Disease - prevention & control; Alzheimer's disease; Apolipoprotein E4 - therapeutic use; apolipoproteins; Biological and medical sciences; blood composition; Canada - epidemiology; Canadian Study of Health and Aging; Cohort Studies; Dementia; diet-related diseases; disease prevention; docosahexaenoic acid; Docosahexaenoic Acids - blood; eicosapentaenoic acid; Eicosapentaenoic Acid - blood; elderly; Epidemiology; Fatty acids; Fatty Acids, Omega-3 - blood; Fatty Acids, Omega-3 - therapeutic use; Feeding. Feeding behavior; fish; Fundamental and applied biological sciences. Psychology; human diseases; human physiology; Humans; Longitudinal Studies; Mercury; Mercury - blood; neurotoxins; omega-3 fatty acids; protein content; Proteins; quantitative analysis; Regression Analysis; risk factors; Studies; Vertebrates: anatomy and physiology, studies on body, several organs or systems
• ISSN: 0002-9165; 1938-3207
• DOI: 10.3945/ajcn.2008.26987

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 ε4 (APOE ε4) status. DESIGN: The CSHA is a cohort study of a representative sample of persons aged greater-than-or-equal65 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 ε4 status. CONCLUSIONS: No associations between n-3 PUFAs and dementia or AD were found. The results regarding mercury may indicate a spurious association.