The efficacy of omega-3 fatty acids on cognitive function in aging and dementia: a systematic review

We systematically reviewed the published literature on the effects of omega-3 fatty acids on measures of cognitive function in normal aging, incidence and treatment of dementia. Computerized databases were searched for published literature to identify potentially relevant studies with the intent to conduct a meta-analysis. We screened 5,865 titles, reviewed 497 studies of which 49 underwent a detailed review, and found 5 studies that pertained to our objectives. We included controlled clinical trials and observational studies, including prospective cohort, case-control, and case series designs; we excluded case reports. We had no language restrictions. We abstracted data on the effects of omega-3 fatty acids and on study design, relevant outcomes, study population, source, type, amount, and duration of omega-3 fatty acid consumption, and parameters of methodological quality. A single cohort study has assessed the effects of omega-3 fatty acids on cognitive function with normal aging and found no association for fish or total omega-3 consumption. In four studies that assessed the effects of omega-3 fatty acids on incidence and treatment of dementia, a trend in favor of omega-3 fatty acids (fish and total omega-3 consumption) toward reducing risk of dementia and improving cognitive function was reported. The available data are insufficient to draw strong conclusions about the effects of omega-3 fatty acids on cognitive function in normal aging or on the incidence or treatment of dementia. However, limited evidence suggests a possible association between omega-3 fatty acids and reduced risk of dementia.