In a new study, experts from Oregon Health and Science University discovered that omega-3 fatty acid docosahexaenoic acid (DHA) supplements did not seem to slow cognitive, functional decline in patients with mild to moderate Alzheimer's disease.
Some studies have found that consumption of DHA, but not other omega-3 fatty acids, is associated with a reduced risk of Alzheimer disease," said Joseph F. Quinn and other colleagues.
However, those studies were observational and did not control who received DHA.
Dr. Quinn and colleagues conducted a randomized, controlled trial to examine whether DHA supplementation would slow the rate of cognitive and functional decline in individuals with Alzheimer's disease.
Participants were randomly assigned to DHA or to identical placebo. Duration of treatment was 18 months. Changes in cognitive and functional abilities were assessed with the Alzheimer's Disease Assessment Scale
"In summary, these results indicate that DHA supplementation is not useful for the population of individuals with mild to moderate Alzheimer disease," the authors wrote.
The researchers added that "because part of the rationale for the trial was epidemiological evidence that DHA use before disease onset modifies the risk of Alzheimer disease, it remains possible that an intervention with DHA might be more effective if initiated earlier in the course of the disease in patients who do not have overt dementia."
The study is published in the November 3 issue of JAMA.