There is no evidence that dietary or supplemental omega 3 polyunsaturated fatty acid (PUFA) reduces the risk of cognitive impairment or dementia in healthy elderly persons without pre-existing dementia

Lim W-S, Gammack JK, Van Niekerk JK, Dangour A

Published Online:

January 21, 2009

Evidence from biological and epidemiological studies suggests that lower omega 3 PUFA intake is associated with an increased risk of dementia. In experimental animal models, dietary enhancement of docosahexanoic acid (a long-chain omega 3 PUFA) slows the expression of Alzheimer's pathology and improves cognitive performance. These findings raise the possibility of similar preventative benefits in humans. Omega 3 PUFA have also being shown to reduce vascular risk, inflammation and oxidative damage. Available clinical studies comparing the occurrence of Alzheimer's disease between elderly persons with different levels of dietary omega 3 PUFA intake, suggest that risk of Alzheimer's disease is significantly reduced among those with higher levels of fish and omega 3 PUFA consumption. However, because these studies are not randomized trials, they provide insufficient evidence to recommend dietary and supplemental omega 3 PUFA for the explicit purpose of dementia prevention.

This review yielded no clinical trials that could confirm or refute the utility of omega 3 PUFA in preventing cognitive impairment or dementia. This is an important area that is in pressing need of further research.

Abstract (click to read)

Background:

Accruing evidence from observational and epidemiological studies suggests an inverse relationship between dietary intake of omega 3 polyunsaturated fatty acid (PUFA) and risk of dementia. Postulated mechanisms that might qualify omega 3 PUFA as an interventional target for the primary prevention of dementia include its anti-atherogenic, anti-inflammatory, anti-oxidant, anti-amyloid and neuroprotective properties.

Objectives:

To review the evidence that omega 3 PUFA supplementation prevents cognitive impairment and dementia in cognitively intact elderly persons.

Search strategy:

The Cochrane Dementia and Cognitive Improvement Group's (CDCIG) Specialized register, MEDLINE, EMBASE,CINAHL PsycINFO, AMED AND CENTRAL and several ongoing trials databases were searched on 5 and 6 October 2005. The CDCIG Register is updated regularly and contains records from all major medical databases and many ongoing trials databases.

Selection criteria:

In order to be selected, trials needed to be randomized, placebo-controlled, doubled blinded, of minimum study duration of 6 months, involved persons aged 60 years and above without pre-existing dementia at study onset, and employed cognitive endpoints.

Data collection and analysis:

Reviewers, working independently, were to select, quality assess and extract relevant data where appropriate and possible. In comparing intervention with placebo, the pooled odds ratios or weighted mean differences and standardized mean difference were to be estimated.

Main results:

There were no randomized trials found in the search that met the selection criteria. Results of two clinical trials are expected in 2008.

Authors' conclusions:

There is a growing body of evidence from biological, observational and epidemiological studies that suggests a protective effect of omega 3 PUFA against dementia. However, until data from randomized trials become available for analysis, there is no good evidence to support the use of dietary or supplemental omega 3 PUFA for the prevention of cognitive impairment or dementia.

This record should be cited as:

Lim W-S, Gammack JK, Van Niekerk JK, Dangour A. Omega 3 fatty acid for the prevention of dementia. Cochrane Database of Systematic Reviews 2006, Issue 1. Art. No.: CD005379. DOI: 10.1002/14651858.CD005379.pub2

Assessed as up to date:

November 12, 2005

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Primary Review Group:

Dementia and Cognitive Improvement Group

Health topics:

Mental health > Dementia & cognition > Cognitive enhancement

Mental health > Dementia & cognition > Prevention: non-cognitively impaired

Neurology > Dementia & cognition > Cognitive enhancement

Neurology > Dementia & cognition > Prevention: non-cognitively impaired

Complementary & alternative medicine > Mental health > Dementia & cognition