No Benefit for DHA in Alzheimer's Disease

Nov. 2, 2010— -- Dietary supplementation with the omega-3 fatty acid "docosahexaenoic acid" (DHA) had no apparent benefit in slowing cognitive decline among patients with mild-to-moderate Alzheimer's disease, according to a large randomized trial.

The 18-month trial among more than 400 patients found that the rate of change -- measured on the cognitive subscale of the Alzheimer's Disease Assessment Scale -- actually increased 7.98 points among those given DHA, compared with 8.27 points among the placebo group, reported Dr. Joseph F. Quinn of Oregon Health and Science University in Portland and colleagues.

Moreover, there was no difference in the rate of change on the Clinical Dementia Rating -- which was an increase of 2.87 points for the DHA supplement group and 2.93 for those on placebo, Quinn and co-authors reported in the Nov. 3 issue of the Journal of the American Medical Association.

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Epidemiologic studies have found that consumption of fish rich in omega-3s and fish oil may help lower the risk of Alzheimer's disease, and animal studies have suggested that the DHA component of omega-3 fatty acids reduced some of the pathologic brain changes.

To assess the potential effects on dementia, Quinn's group enrolled 402 patients with mild-to-moderate disease and low DHA levels from 51 participating centers around the U.S., randomizing them to 2 g/day of DHA or to placebo.

A subset of patients underwent MRI at baseline and again at 18 months, and there was no difference between the groups on decline in total brain volume.

There also was no difference in percentage of brain volume decline, or in volume declines seen in the left or right regions of the hippocampus.

The investigators also considered whether there would be differences according to baseline dementia severity, and again found that the rate of change was similar.