Effect of Omega-3 Polyunsaturated Fatty Acid Supplements on Cognitive Performance in Patients with Mild Cognitive Impairment or Alzheimer's Disease: A Systematic Review and Meta-Analysis.

Context: A positive effect of omega-3 polyunsaturated fatty acids (n-3 PUFAs) on brain activity has been observed within subjects who have Alzheimer's disease (AD) or mild cognitive impairment (MCI). However, inconsistent findings have been reported regarding the efficacy or ineffectiveness of an n-3 PUFA dietary intervention for cognitive improvement.

Objective: To address this problem, our thorough investigation and statistical analysis sought to assess the impact of n-3 PUFA dietary intake on cognitive function among persons diagnosed with AD or MCI.

Data sources: The databases consulted included PubMed, PubMed Central Library, and the Cochrane Library.

Data extraction: Nine articles reporting on the findings of randomized controlled trials that looked at the link between n-3 PUFA intake and cognitive performance-related outcomes were included in the comprehensive evaluation, with the meta-analysis utilizing 7 of these. Key details such as author, publication year, study area, research type, pathology (MCI or AD), were incorporated into the data extraction procedure.

Data analysis: Evaluation of the included studies used Cochrane risk-of-bias instruments, a random-effects model, standardized mean differences (SMDs) and 95% CIs.

Results: Our findings have provided evidence of the effectiveness of an n-3 PUFA treatment in improving Full-Scale IQ (FSIQ) (SMD -0.82; 95% CI: -1.57, -0.08; P = .000), information processing (SMD -2.90; 95% CI: -5.25, -0.56; P = .000), and digit span/working memory/attention aspects of cognitive functioning (SMD -1.89; 95% CI: -3.27, -0.51; P = .000). No evidence was found for the effectiveness of an n-3 PUFA treatment in improving image completion (SMD -0.07; 95% CI: -0.50, 0.35; P = .000), picture layout (SMD -0.08; 95% CI: -0.32, 0.16; P = .075), block design SMD -0.15; 95% CI: -0.37, 0.03; P = .123), or arithmetic aspects of cognitive functioning (SMD -0.33; 95% CI: -0.61, 0.04; P = .007).

Conclusion: In summary, n-3 PUFAs have been found to significantly affect some domains of cognitive function, such as FSIQ, information processing, and digit span/working memory/attention in subjects with MCI. However, no significant effect was observed for some domains, such as picture completion, picture arrangement, or block design.