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Review
. 2015 Mar 18;10(3):e0120391.
doi: 10.1371/journal.pone.0120391. eCollection 2015.

Docosahexaenoic Acid and Adult Memory: A Systematic Review and Meta-Analysis

Affiliations
Free PMC article
Review

Docosahexaenoic Acid and Adult Memory: A Systematic Review and Meta-Analysis

Karin Yurko-Mauro et al. PLoS One. .
Free PMC article

Abstract

Introduction: Subjective memory complaints are common with aging. Docosahexaenoic acid (DHA; 22:6 n-3) is a long-chain polyunsaturated fatty acid (LCPUFA) and an integral part of neural membrane phospholipids that impacts brain structure and function. Past research demonstrates a positive association between DHA plasma status/dietary intake and cognitive function.

Objectives: The current meta-analysis was designed to determine the effect of DHA intake, alone or combined with eicosapentaenoic acid (EPA; 20:5 n-3), on specific memory domains: episodic, working, and semantic in healthy adults aged 18 years and older. A secondary objective was to systematically review/summarize the related observational epidemiologic literature.

Methods: A systematic literature search of clinical trials and observational studies that examined the relationship between n-3 LCPUFA on memory outcomes in healthy adults was conducted in Ovid MEDLINE and EMBASE databases. Studies of subjects free of neurologic disease at baseline, with or without mild memory complaints (MMC), were included. Random effects meta-analyses were conducted to generate weighted group mean differences, standardized weighted group mean differences (Hedge's g), z-scores, and p-values for heterogeneity comparing DHA/EPA to a placebo. A priori sub-group analyses were conducted to evaluate the effect of age at enrollment, dose level, and memory type tested.

Results: Episodic memory outcomes of adults with MMC were significantly (P<.004) improved with DHA/EPA supplementation. Regardless of cognitive status at baseline, > 1 g/day DHA/EPA improved episodic memory (P<.04). Semantic and working memory changes from baseline were significant with DHA but no between group differences were detected. Observational studies support a beneficial association between intake/blood levels of DHA/EPA and memory function in older adults.

Conclusion: DHA, alone or combined with EPA, contributes to improved memory function in older adults with mild memory complaints.

Conflict of interest statement

Competing Interests: KYM is currently employed by DSM Nutritional Products. DSM Nutritional Products produces and sells nutritional oils rich omega-3 and omega-6 fatty acids, vitamins and other nutritional ingredients. Dr. Yurko-Mauro provided interpretation of data, critical revision, and final approval of the manuscript. MVE is an employee of Van Elswyk Consulting Inc. and receives compensation from DSM Nutritional Products and other companies to provide consulting services. Service for this manuscript included literature screening, data extraction, critical revision, editing, and final approval of the manuscript. DA is an employee of EpidStat Institute and a former employee of Exponent, Inc. and received compensation from DSM Nutritional Products for statistical analysis of data, interpretation of data, editing, and final approval of the current manuscript.

Figures

Fig 1
Fig 1. Flow Diagram of Study Selection.
Fig 2
Fig 2. Forest plot with meta-analysis of episodic memory data.
Episodic memory data from pertinent human intervention studies (n = 5) of DHA supplementation in adults with mild memory complaints. *Asterisks denote study included more than one test of episodic memory, results for each episodic memory test within a given study represented individually. Summary statistics are as follows z = 1.932 (p = 0.053); Hedge’s g z = 2.86 (p = 0.004).
Fig 3
Fig 3. Forest plot with meta-analysis of dose and episodic memory.
Episodic memory data from pertinent human intervention studies (n = 6) of DHA supplementation alone or in combination with EPA > 1g in all adults. *Asterisks denote study included more than one test of episodic memory, results for each episodic memory test within a given study represented individually. Summary statistics are as follows z = 1.81 (p = 0.070); Hedge’s g z = 2.05 (p = 0.04).

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Substances

Grant support

DSM Nutritional Products provided funding for the preparation of this manuscript. The funders had no role in data collection or analysis but contributed to study design and manuscript preparation as KYM is an employee of DSM Nutritional Products.
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