This study investigated the role of LCn-3PUFA in global cognitive function among healthy and Alzheimer's disease (AD) elders considering their baseline cognitive performance.

Cognitive decline is a core feature of the aging brain. Supplementation with Omega-3 long-chain polyunsaturated fatty acids (LCn-3PUFA) is widely used to manage dementia among elders, however the conflict about its effectiveness.

Five electronic databases were searched (PubMed, Scopus, Web of Science, Cochrane library, and Embase) for healthy or AD elders above 60 years old receiving LCn-3PUFA as a capsule supplementation, only randomized clinical trials that assess the global cognitive function were included, we investigated the global cognitive function by the mini-mental state examination scale (MMSE).

A total of 7409 citations were identified of which 13 citations were included in the final synthesis. The pooled Cohen’s d of MMSE favored the omega arm over the control arm in global cognitive performance (Cohen’s d -0.19, 95% CI (-0.27 to -0.10), P<0.001), however, the studies were not homogeneous, the subgroup analysis showed that only healthy elders receiving LCn-3PUFA had significant results while no significant change was found among AD patients (Cohen’s d -0.20, 95% CI (-0.29 to -0.11), P<0.001), (Cohen’s d -0.14, 95% CI (-0.36 to 0.09), P=0.16) respectively. Another subgroup analysis based on the baseline cognitive performance revealed that only healthy elders with no cognitive impairment showed significant results that favored the omega group (Cohen’s d -0.23, 95% CI (-0.33 to -0.13), P<0.001), however, no significant change were recorded in elders with cognitive impairment ranging from mild to moderate (Cohen’s d -0.08, 95% CI (-0.25 to 0.09), P=0.33).

Healthy elders with normal cognitive performance showed a significant benefit from LCn-3PUFA in global cognitive function, however, no significant change was recorded among elders with mild to moderate cognitive impairment or among elders with AD.