A Disappointing Result for Omega-3 in Alzheimer’s

There have been some studies suggesting that the omega-3 fatty acid docosahexaenoic acid (DHA) might lower the risk for Alzheimer’s disease, so researchers conducted a randomized trial to see if DHA would slow cognitive decline in patients with the disease.  The results are published in the Journal of the American Medical Association.   

US researchers randomized some 400 adults with mild-to-moderate Alzheimer’s at 51 clinical research sites to take DHA (2 g daily) or a matching placebo for 18 months.  Two well recognized Alzheimer rating scales - the Alzheimer's Disease Assessment Scale and the Clinical Dementia Rating Sum of Boxes – were administered before and after 18 months’ treatment.  Approximately 25% of the participants had volumetric MRI done to measure brain atrophy. 

At the end of treatment, there was no difference between the DHA and placebo groups in the rate of cognitive decline, as measured by both rating scales, and the total brain volume was unaltered by DHA administration.  The authors of the report conclude that "there is no basis for recommending DHA supplementation" for patients with Alzheimer’s disease.

This is a disappointing result, and it goes against the earlier animal and epidemiological studies showing that omega-3 fatty acids appear to influence the development of the disease.  However, it will not discourage the numerous elder citizens who already consume omega-3 supplements.  Some may question why DHA, and not a mixture of DHA and eicosapentaenoic acid (EPA) was used in the study.  DHA is a longer-chain fatty acid, and is found in the brain, unlike EPA.  However, sorting out the omega-3 fatty acids is not easy.  And who knows if taking them before symptoms of dementia appear, i.e. in the progressive or even the earlier, mild cognitive impairment phase, might not produce a more favorable result?  I doubt the interest in omega-3s will end here.

P.S.  No sooner had I written this, than a new study was reported in Alzheimer’s & Dementia.  Healthy elderly adults with age-related cognitive decline were given 900 mg DHA or placebo, daily for 24 weeks.  Learning/memory ascores improved significantly with DHA, compared to those with placebo, and the improvement correlated with blood DHA levels.  There were some weaknesses in the study design and analysis, but it shows that omega-3s are far from a dead issue when given early in mild cognitive impairment.