Omega-3 fatty acids and cognitive decline: a systematic review

In a growing elderly population, mild cognitive impairment (MCI) and age related cognitive decline (ARCD) are increasing in prevalence worldwide. In the search for food compounds able to ameliorate this condition, it has been postulated that n-3 Long chain polyunsaturated fatty acids (n-3 LCPUFA), also known as omega-3, consumption could have a positive effect in the prevention or therapy of these cognitive declines. However, there are contradictory findings in the literature concerning the effects of n-3 LCPUFA on cognitive decline making it difficult to draw a conclusion on this topic. This current systematic review studies the relationship between n-3 LCPUFAs and cognitive status in aged adult and elder populations to determine whether there is or not a positive effect of n-3 LCPUFAs supplementation on cognitive decline. Additionally, we remark how duration periods, different cognitive baseline status in subjects, dosage of n-3 LCPUFAs administration and the presence of other factors might be related to different outcomes. A search of randomized controlled trials (RCTs) related with the relationship between cognitive impairment and n-3 LCPUFA (docosahexaenoic acid, eicosapentanoic acid or combined) supplementation was conducted through PubMed database from January 2010 to December 2017 following the PRISMA statement. Interventional studies which included aged adults or elder subjects with or without MCI and with no previous intake of fish oil supplements (FOS) were included. Ten out of the fourteen RCTs reviewed showed positive outcome on at least one domain of cognitive function (working memory, executive function, verbal memory, short-term memory, perceptual speed, etc.). This systematic review concludes that omega-3 supplementation might have a positive effect on cognitive function. Thus, n-3 LCPUFAs could be used as a preventive or therapeutic tool for cognitive decline in aged or elder adults.