Researchers report that those with mild/moderate Alzhimer’s Disease symptoms who received omega-3 DHA fatty acid (docosahexaenoic acid) over an 18-month period experienced the same rates of cognitive and functional decline as those on a placebo. Their study has been published in today’s issue of JAMA (Journal of the American Medical Association) which focuses on aging this week. The scientists had been hoping for encouraging results because fish oils have been linked to a lower risk of dementia and cognitive decline.

Cognition refers to the process of being aware, thinking, knowing, judging and learning. Cognitive decline refers to lower awareness, knowing, judging, learning and thinking. People with Alzheimer’s disease experience progressive cognitive decline.

Joseph F. Quinn, M.D., of Oregon Health and Science University and the Portland VA Medical Center, Portland, Ore., said:

Several studies have found that consumption of fish, the primary dietary source of omega-3 fatty acids, is associated with a reduced risk of cognitive decline or dementia. Some studies have found that consumption of DHA, but not other omega-3 fatty acids, is associated with a reduced risk of Alzheimer disease.

However, those studies did not control who was given DHA. The authors add that previous studies were observational. Animal studies did show that those given DHA had lower Alzheimer-like brain pathology.

Dr. Quinn and team carried out a controlled, randomized clinical trial to determine whether DHA supplements might slow down the rate at which Alzheimer’s patients’ cognitive and functional decline advanced. It involved 402 patients with mild/moderate Alzheimer’s disease at 51 clinical research centers in the USA from November 2007 to May 2009.

The patients were randomly selected to receive identical daily 2 gram tablets that either had DHA or a placebo. 60% got the DHA while 40% were given the placebo.

During the 18-month trial, alterations in functional and cognitive abilities were gauged with the ADAS-cog (Alzheimer’s Disease Assessment Scale) and the CDR (Clinical Dementia Rating) sum of boxes. Brain atrophy rates were also measured using MRI scans with a number of patients.

171 DHA patients and 124 on a placebo completed the trial (295 total). The ADAS-cog score was not affected by DNA supplementation, the researchers found – average scores were 8.27 for those on the placebo and 7.98 for patients on DHA. The CDR sum of boxes change over the trial period was 2.87 for the DHA group and 2.93 for the placebo group.

102 patients had had an MRI scan at the beginning and the end of the study, 53 from the DHA group and 49 from the placebo group. DHA was found to have no effect on total brain volume during the trial period.

The authors wrote:

In summary, these results indicate that DHA supplementation is not useful for the population of individuals with mild to moderate Alzheimer disease.

..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.

In an accompanying JAMA Editorial, Dr. Kristine Yaffe, of the University of California, San Francisco and Veterans Affairs Medical Center, San Francisco, wrote:

his trial adds to a growing literature that treatment with DHA does not improve symptoms of AD. Although several observational studies reported that diets rich in fish or supplements with omega-3 fatty acids were associated with reduced risk of developing AD, most randomized clinical trials for treatment of AD or mild cognitive impairment or in healthy elderly individuals have not found a beneficial effect.

“Docosahexaenoic Acid Supplementation and Cognitive Decline in Alzheimer Disease – A Randomized Trial”
Joseph F. Quinn, MD; Rema Raman, PhD; Ronald G. Thomas, PhD; Karin Yurko-Mauro, PhD; Edward B. Nelson, MD; Christopher Van Dyck, MD; James E. Galvin, MD; Jennifer Emond, MS; Clifford R. Jack Jr, MD; Michael Weiner, MD; Lynne Shinto, ND; Paul S. Aisen, MD
JAMA. 2010;304(17):1903-1911. doi:10.1001/jama.2010.1510

Written by Christian Nordqvist