Low Plasma N-3 Fatty Acids and Dementia in Older Persons: The InCHIANTI Study

There is growing evidence linking polyunsaturated fatty acids (FA) of the omega-3 family (n-3 FA) to cognitive function in humans (1). Prospective epidemiological studies found that a low dietary intake of fish, the major source of long-chain n-3 FA (2,3), as well as a low intake of n-3 FA in general (4), was associated with higher risk of developing cognitive impairment and dementia. However this prospective association was not confirmed by other studies (5). Plasma FA levels are good markers of dietary intake (6). Although plasma FA have been usually considered markers of short-term intake, recent studies show that they also reflect long-term intake (7), because their levels are consistent with changes in FA composition of adipose tissue. Moreover, circulating levels might be a better measure of exposure than dietary intake because they are less liable to lack precision and potential biases typical of food frequency questionnaires. Studies that explored the relationship between plasma FA and cognitive function found that individuals with dementia tend to have low plasma levels of n-3 FA (8,9). A lower proportion of n-3 FA in the erythrocyte membranes was predictive of cognitive decline (10). In contrast, a recent Canadian study failed to detect any association between plasma n-3 FA and both prevalence and incidence of cognitive impairment and dementia (11). Due to these conflicting results, it is unclear whether low plasma levels of n-3 FA are associated with cognitive impairment (12). The aim of our study was to evaluate the relationship between plasma FA and dementia in a large sample of older participants enrolled in the InCHIANTI study.