Based upon 14 studies (one case control, three cross-sectional, six prospective cohort and four RCT studies) primarily of healthy elderly subjects or those matched for incident dementia, results are mixed. Six of the 14 studies found a positive association of EPA, DHA or fish consumption and a decreased risk of cognitive decline. The majority of the studies included large populations of elderly subjects measuring either blood levels of EPA and DHA and fish consumption. Results vary based on dose of supplementation or dietary consumption of fish, EPA or DHA. Further research is needed to determine whether EPA, DHA and fish consumption has a protective effect for all-cause dementia. There is some evidence that ApoE e4 carrier status should be factored into future studies.

• Grade I means there is Good/Strong evidence supporting the statement;
• Grade II is Fair;
• Grade III is Limited/Weak;
• Grade IV is Expert Opinion Only;
• Grade V is Not Assignable.
• High (A) means we are very confident that the true effect lies close to that of the estimate of the effect;
• Moderate (B) means we are moderately confident in the effect estimate;
• Low (C) means our confidence in the effect estimate is limited;
• Very Low (D) means we have very little confidence in the effect estimate.
• Ungraded means a grade is not assignable.