Does DHA slow progression of Alzheimer’s disease?

January 01, 0001

Does DHA slow progression of Alzheimer’s disease?

Epidemiological and animal studies have suggested that consumption of docosahexaenoic acid (DHA) may reduce the risk of Alzheimer’s disease. These US researchers examined whether supplementation with DHA slows cognitive and functional decline in individuals with Alzheimer disease. They performed a randomized, double-blind, placebo-controlled trial using DHA supplementation in patients with mild to moderate Alzheimer disease (Mini- Mental State Examination scores, 14-26) enrolled from sites of the Alzheimer’s Disease Cooperative Study. Enrollees (n=402, though only 295 completed the study) were randomly assigned to algal DHA (2 g/d) or to identical placebo for 18 months. Cognition and functioning were followed using the cognitive subscale of the Alzheimer’s Disease Assessment Scale (ADAS-cog) and change in the Clinical Dementia Rating (CDR). Rates of brain atrophy were measured using volumetric magnetic resonance imaging in a subsample of participants (n = 102).

The researchers found: "Supplementation with DHA had no beneficial effect on rate of change on ADAS-cog score, which increased by a mean of 7.98 points for the DHA group during 18 months vs 8.27 points for the placebo group. The CDR sum of boxes score increased by 2.87 points for the DHA group during 18 months compared with 2.93 points for the placebo group. In the subpopulation of participants (DHA: 53, placebo: 49), the rate of brain atrophy was not affected by treatment with DHA. Individuals in the DHA group had a mean decline in total brain volume of 24.7 cm3 during 18 months and a 1.32% volume decline per year compared with 24.0 cm3 for the placebo group during 18 months and a 1.29% volume decline per year."

The researchers concluded: "Supplementation with DHA compared with placebo did not slow the rate of cognitive and functional decline in patients with mild to moderate Alzheimer disease."

Unfortunately, DHA does not appear to be a useful treatment once Alzheimer’s disease has been diagnosed.

For the full abstract, click here.

JAMA 304(17):1903-1911, 3 November 2010 © 2010 American Medical Association
Docosahexaenoic Acid Supplementation and Cognitive Decline in Alzheimer Disease: A Randomized Trial. Joseph F. Quinn, Rema Raman, Ronald G. Thomas, et al.

Category: N. Neurological. Keywords: docosahexaenoic acid, DHA, Alzheimer’s, dementia, cognition, functioning, randomized controlled trial, journal watch.
Synopsis edited by Dr Paul Schaefer, Toledo, Ohio. Posted on Global Family Doctor 26 November 2010

Pearls are an independent product of the Cochrane primary care group and are meant for educational use and not to guide clinical care.