Key Findings:
Lower n-3 and higher n-6 PUFAs may be associated with depression, dementia and cognitive decline. Erythrocyte membrane EPA, DPA, and total n3 PUFA concentrations were positively and AA/EPA ratios were negatively associated with global cognitive function in a sample of older people with previous major depression. Erythrocyte ALA and n3 PUFAs concentrations were positively associated with immediate verbal memory. ALA deficiency may aggravate the composition and physicochemical properties of brain cell membranes, neurons, oligodendrocytes, and astrocytes, which results in neurosensory and behavioral upset. Lower concentrations of n3 PUFAs or ALA in erythrocyte membranes may be predictors of cognitive impairment in people with late-life depression and other cognitive issues.
ABSTRACT:
Lower concentrations of n3 PUFAs have been reported to be associated with cognitive impairment and dementia, but also with depression, itself a potential risk factor for cognitive decline. The aims of this study were to investigate associations between n3 PUFA concentrations in erythrocyte membrane or plasma and cognitive function in an at risk sample of older people with previous major depression and to explore specificity with respect to cognitive domains. A cross sectional sample of 132 eligible participants who had recovered from major depression (mean and SD age: 67.8 and 6.6 y) were enrolled from outpatient psychiatric services. A series of cognitive tests and a structured questionnaire were administered. Fasting blood samples were collected for n3 PUFA measurements. Higher EPA and total n3 PUFA concentrations and a lower ratio of arachidonic acid to EPA in erythrocyte membranes were associated with a higher cognitive composite score: independent of age and sex, but no longer significant after adjustment for education. No associations were found with plasma concentrations of any fatty acid. Considering individual cognitive tests, the strongest and most consistent correlations were found between immediate recall and concentrations of total n3 PUFAs and alpha linolenic acid (ALA) in erythrocytes, which were observed only in participants with recurrent depression. Total erythrocyte n3 PUFA concentrations are positively associated with cognitive function, particularly immediate recall, in older people with previous depression. Lower concentrations of n3 PUFAs or ALA in erythrocyte membranes may be good predictors for cognitive impairment in older people with previous recurrent depression. (Authors abstract)
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