Long-chain omega-3 polyunsaturated fatty acids and cognitive decline in non-demented adults: a systematic review and meta-analysis

Abstract

Context Long-chain omega-3 polyunsaturated fatty acids (LCn-3PUFAs) are widely considered as nootropic agents that may be beneficial in reversing cognitive impairment. Objective The present systematic review of randomized controlled trials was conducted to determine the changes in cognitive function after intervention with LCn-3PUFA supplementation in non-demented adults, including those with mild cognitive impairment. Data Sources Five databases (MEDLINE, CINAHL, Scopus, EMBASE, and the Cochrane Library) were searched systematically along with reference lists of selected articles. Study Selection Studies were eligible for inclusion if they measured the effect of LCn-3PUFA supplementation on cognition in non-demented adults. Data Extraction A total of 787 records were screened, of which 25 studies were eligible for inclusion. Treatment effects were summarized as global cognitive function for primary outcome and measured using the Mini-Mental State Examination and individual cognitive domains for secondary outcome. The pooled effect sizes were estimated using Hedge’s g and random-effects modeling. Data Analysis Results from randomized controlled trials indicate that LCn-3PUFAs have no effect on global cognitive function (Hedge’s g = 0.02; 95% confidence interval, −0.12 to 0.154), and among the specific cognitive domains, only memory function showed a mild benefit (Hedge’s g = 0.31; P = 0.003; z = 2.945). Conclusion The existing literature suggests that LCn-3PUFA supplementation could provide a mild benefit in improving memory function in non-demented older adults. Systematic Review Registration PROSPERO registration no. CRD42017078664.

Why Have the Benefits of DHA Not Been Borne Out in the Treatment and Prevention of Alzheimer’s Disease? A Narrative Review Focused on DHA Metabolism and Adipose Tissue

“…This group found that supplementation with LCPUFA was associated with mild improvements in memory, however, with heterogeneity and asymmetry suggestive of publication bias. In agreement with historical systematic reviews, these analyses found no effect of LCPUFA upon specific cognitive domains such as visuospatial function or wider tests of global cognitive assessment [ 92 ]. In a similar meta-analysis, Zhang et al [ 93 ] analyzed the effects of N3 PUFA supplementation upon cognitive function in individuals aged >65 years with established mild cognitive impairment (MCI).…”

Expert Opinion on Benefits of Long-Chain Omega-3 Fatty Acids (DHA and EPA) in Aging and Clinical Nutrition

“…However, there are relatively few trials and these differ in the dose of DHA and EPA and type of placebo used, the duration of supplementation, sample size, the severity of cognitive decline at baseline as well as the omega-3 LCPUFA status of the participants (where this was even assessed) and the cognitive outcomes/tests used. Supplementation with omega-3 LCPUFAs had a small effect on memory [60] and executive function [61] in non-demented older people. A meta-analysis of three randomized, placebo-controlled trials with omega-3 LCPUFA supplements found no effect on severity of dementia, quality of life or mental health in patients with mild or moderate Alzheimer's disease over 6, 12 and 18 months [62].…”

Self-Reported Omega-3 Supplement Use Moderates the Association between Age and Exercising Cerebral Blood Flow Velocity in Older Adults

“…Regardless of the mechanism through which omega-3 supplement use stabilizes CBF, the consequent increased delivery of oxygen and nutrients to the brain could explain findings from other studies that show omega-3 fatty acids augment cognitive function and prevent cognitive decline [39][40][41][42]. For example, the connection between atherosclerosis and dementia has been well-established [43], and a meta-analysis of randomized controlled trials showed that omega-3 fatty acids significantly slowed the progression of atherosclerosis [44], suggesting that omega-3 fatty acids could potentially prevent cognitive decline through improvements in vascular health.…”