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Full Title: Effects of Omega-3 Fatty Acids on Cognitive Function with Aging, Dementia, and Neurological Diseases
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Objectives: To assess the evidence for beneficial effects of omega-3 fatty acids on:
- Cognitive function in normal aging.
- The incidence of dementia.
- Treatment of dementia.
- The incidence of several neurological diseases.
- Clinical outcomes related to the progression of multiple sclerosis (MS).
Data Sources: Computerized databases were searched to identify potentially relevant studies and industry experts were contacted for unpublished data.
Review Methods: After screening 5,865 titles and reviewing 497 studies, the researchers found 12 relevant studies. These included controlled clinical trials (whether randomized or not) and observational studies, including prospective cohort, case-control, and case series designs; case reports were excluded. There were no language restrictions. Data was abstracted on the effects of omega-3 fatty acids; study design; relevant outcomes; study population; source, type, and amount of consumed omega-3 fatty acid; duration of consumption; and parameters of methodologic quality.
- A single cohort study of omega-3 fatty acids found no association for fish or total omega-3 consumption with cognitive function during normal aging.
- In four studies that assessed the effects of omega-3 fatty acids on incidence and treatment of dementia (three prospective cohort studies and one randomized, controlled trial [RCT]), a trend was reported in favor of reduced dementia risk and improved cognitive function with increased dietary omega-3 fatty acids (fish and total omega-3 consumption).
- Two studies (one cohort and one case-control) that assessed the effects of omega-3 fatty acids on the incidence of MS were inconclusive. A single cohort study evaluating the effects of omega-3 fatty acids on the incidence of Parkinson's disease found no significant association between dietary intake and reduced incidence. Another case-control study found a statistically significant association between weekly maternal fish consumption throughout pregnancy and reduced risk of cerebral palsy in the offspring.
- In one RCT, omega-3 fatty acids (fish, ALA, EPA, DHA) had no effect on the progression of MS; two single-arm, open-label trials showed improvement in MS-related disability with omega-3 supplementation.
Conclusions: The quantity and strength of evidence for effects of omega-3 fatty acids on the neurological conditions assessed vary greatly. The small number of studies that met the inclusion criteria suggest that a great deal of epidemiological and clinical research remains to be done before any strong conclusions can be drawn or policy recommendations can be made regarding the neurological health effects of omega-3 fatty acids.
Effects of Omega-3 Fatty Acids on Cognitive Function with Aging, Dementia, and Neurological Diseases
Evidence-based Practice Center: Southern California
Topic Nominator: Office of Dietary Supplements, National Institutes of Health
Current as of February 2005