Blood Levels of EPA and Decreased Risk of Dementia
Samieri C et al., Am. J. Clin. Nutr. 88 :714-721, 2008.
Equipe Epidemiologie de la Nutrition et des Compartements Alimentaries, Bordeaux, France
Population studies have indicated that elderly individuals who are regular fish consumers (thereby having higher intakes of DHA/EPA) have a decreased risk for dementia and Alzheimer disease. Food records and dietary recalls often result in inaccurate and inconsistent estimations of omega-3 fatty acid intakes. Consequently, epidemiologists have often employed biomarkers for better assessing omega-3 status in the populations by measuring blood levels of EPA, DHA, and other fatty acids in blood serum samples. The present longitudinal study was conducted to determine whether plasma omega-3 fatty acids may possibly predict the eventual risk for incident dementia in a cohort of older persons independently of their depressive status.
The present study was conducted among participants from 3 cities in France and included 9294 community dwellers who had to be aged ≥65 years and not institutionalized. The baseline data collection included a wide range of informative parameters including neuropsychological testing and blood samplings with two follow-up examinations conducted at 2 and 4 years after the baseline examination. The diagnosis of dementia was derived from a 3-step procedure using trained psychologists who administered various neuropsychological tests at baseline and at follow-up including examination of all participants by a neurologist at baseline. Depressive symptomology was assessed using appropriate baseline home interviews and the validated Centre for Epidemiological Studies- Depression (CES-D) scale-considered to be a valid reliable measure of depressive symptomology in elderly persons. The results indicated that a higher level of EPA (eicosapentaenoic acid) in the plasma (lipid) samples was associated with a significantly lower incidence of dementia (by 31% overall, hazard ratio of 0.69) independently of depressive status and after adjusting for age, education, diabetes, and other parameters. Interestingly, the relations between DHA levels and total omega-3 fatty acid levels in plasma and incident dementia did not maintain statistical significance using multivariate models. However, higher ratios of arachidonic acid:DHA and n-6:n-3 fatty acids were related to an increased risk of dementia-particularly in depressive subjects. The investigators conclude that a high plasma EPA concentration may decrease the risk of dementia and that further research on the role of EPA in this condition is deserving of further research.
Dr. Holub's Comments:
The present results are of particular interest since DHA is the omega-3 fatty acid found in high concentrations in membrane phospholipid components of neural membranes where it is recognized as playing an important role in brain signal transduction and resulting functionality. It is possible that EPA may have specific effects on neuroprotection during the aging process as either complimentary or independent to those of DHA. It should also be recognized that higher levels of EPA in the body (based on the blood measures) may elicit improvements in blood flow and anti-inflammatory properties which could underlie some of the previously-recognized benefits of fish consumption (containing DHA+EPA) with respect to the risk of dementia in aging populations. Future studies will need to determine the optimal levels of EPA in the circulation and corresponding optimal intakes of dietary EPA for decreasing the risk of dementia in the elderly. EPA in the body can be derived from the direct consumption of EPA from fish/functional foods/supplements. EPA can also be formed to some limited extent from dietary alpha-linolenic acid (LNA) via desaturation/elongation reactions. Finally, some DHA can be transformed into EPA via metabolism (sometimes referred to as ‘retroconversion’) in the human body to a somewhat limited extent (Conquer and Holub. J. Nutr. 126:3032-3039, (2006)).