The study by Schaefer et al in this issue of Archives of Neurology1 is an important contribution to a young field of study on diet and neurodegenerative diseases. The authors found lower 9-year risk of incident Alzheimer disease among persons with higher levels of plasma phosphatidylcholine docosahexaenoic acid (DHA). The association was specific to DHA as none of the other ω-3 fatty acids was associated with Alzheimer disease risk. In a subset of their cohort, fish consumption was positively correlated with plasma DHA but was not statistically significantly associated with incident Alzheimer disease. However, it is possible that the analysis was underpowered to observe a protective association of fish consumption, as the inverse relative risk was based on a relatively small subsample of 488 subjects.
Morris MC. Docosahexaenoic Acid and Alzheimer Disease. Arch Neurol. 2006;63(11):1527-1528. doi:10.1001/archneur.63.11.1527