Fatty Acid's Role in Alzheimer's Remains In Doubt

Once Alzheimer's starts its relentless march through the brain, the omega-3 fatty acid DHA did not appear capable of slowing it down.

This disappointing result was reported at the Alzheimer's Association 2009 International Conference on Alzheimer's Disease, held in Vienna in July.

The result emerged from a National Institute on Aging–funded trial designed to test the hypothesis that the omega-3 fatty acid docosahexaenoic acid (DHA) would slow the rate of disease progression in Alzheimer's patients with mild to moderate symptoms.

The lead investigator was Joseph Quinn, M.D., an associate professor of neurology at Oregon Health and Science University.

Some 400 subjects with probable mild or moderate Alzheimer's (with a Mini-Mental State Exam score of 14-26) were randomized to receive two grams of DHA or a placebo each day for 18 months. Subjects in both groups were assessed for mental function, global dementia severity status, activities of daily living, and behavioral symptoms both at the start of the study and at the end of 18 months. Subjects' scores at the start and end of the trial were compared. So were outcomes for the DHA and placebo groups.

Subjects taking DHA showed both increased blood levels and increased cerebrospinal fluid levels of DHA. Nonetheless, the treatment did not slow a decline in their cognitive function and behavior.

Quinn and his colleagues then conducted a second leg of their study. This time they looked to see whether DHA could slow Alzheimer's depending on whether their subjects carried the APOE-e4 gene variant known to increase risk for the disease. Again the finding was negative.

Thus, “DHA is not recommended for the treatment of Alzheimer's disease,” Quinn told Psychiatric News.

However, it is still “possible, but as yet unproven,” that DHA can help prevent Alzheimer's, Quinn said. He was referring to a study reported in the November 2006 Archives of Neurology. This study found that older people with higher levels of DHA in their blood were less susceptible to Alzheimer's and other forms of dementia than were older people with lower levels of DHA in their blood (Psychiatric News, January 5, 2007).

And even if DHA cannot slow or prevent Alzheimer's, it may still be able to boost the memory of seniors without Alzheimer's. The reason? A study also reported at the international Alzheimer's conference last month found that DHA had a modest, but significant positive impact on memory in older subjects without Alzheimer's.

In this study, Karin Yurko-Mauro, Ph.D., associate director of clinical research at Martek Biosciences Corporation in Columbia, Md., and colleagues randomized 485 older subjects without Alzheimer's, but with normal age-related memory complaints such as difficulty remembering names or appointments, to receive either 900 mg a day of DHA or a placebo for six months. Subjects were evaluated both at the start and end of the trial with an instrument that discriminates well between aging, mild cognitive impairment, and Alzheimer's and that is sensitive to early episodic memory changes. Results between the two groups were compared.

The DHA group made significantly fewer memory errors on the test at the end of the trial than they had at the start, which was not the case for the placebo group. Moreover, DHA showed an excellent safety profile in this older population.

The findings of this study “indicate that the use of 900 mg of . . . DHA per day improves learning and memory recall in healthy aging adults with mild memory complaints,” Yurko-Mauro told Psychiatric News.

Details about the Clinical Trial of Docosahexanoic Acid (DHA) for the Treatment of Alzheimer's Disease are posted in video form at<www.alz.org/icad/icad_video_quinn.asp>. Details on the results of the Memory Improvement With DHA Study are posted in video form at<www.alz.org/icad/icad_video_yurko-mauro.asp>.▪