A clinical trial of docosahexanoic acid (DHA) for the treatment of Alzheimer's disease

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Background: Epidemiologic studies and animal studies suggest that supplementation with the omega 3 fatty acid, docosahexanoic acid (DHA), will slow the rate of neurodegeneration in Alzheimer's disease (AD). The excellent safety profile of DHA was also a consideration in designing a clinical trial in AD. Methods: A double blind, randomized, placebo-controlled clinical trial comparing DHA and placebo in AD patients was conducted by the National Institute on Aging Alzheimer's Disease Cooperative Study Unit. Fifty one sites in the United States enrolled 402 subjects between February and November 2007. Subjects had a diagnosis of probable AD with Mini-mental state exam score (MMSE) 14-26, and dietary DHA intake of ≤ 200 mg per day. Subjects were treated with DHA or placebo at a dose of 2 grams per day for 18 months, with the final subjects completing clinical activity in May 2009. Co-primary outcomes were rate of change on Alzheimer's disease assessment scale-cognitive (ADAS-cog) and rate of change on Clinical Dementia Scale-sum of the boxes (CDR-SOB). Results: The study population was 52.2% female with a mean age of 76 ± 8.7 years, mean education of 14.3 ± 2.8 years, and mean MMSE = 20.7 ± 3.6, with 59% ApoE4 positive and 41% ApoE4 negative. Mean plasma DHA at baseline was 3.15 ± 1.12 weight percent. Conclusions: A trial of DHA supplementation for mild to moderate AD will be completed in May 2009. Recruitment was completed ahead of schedule. The criteria for baseline dietary DHA consumption yielded a baseline plasma DHA level which will permit significant increases with supplementation. The primary analysis of the efficacy (ie, rate of change on ADAS-cog and CDR-SOB) and safety of DHA supplementation in patients with mild to moderate AD will be presented.