Associations between n-3 PUFA concentrations and cognitive function after recovery from late-life depression
Associations between n-3 PUFA concentrations and cognitive function after recovery from late-life depression
Year: 2012
Authors: Chiu, C.-C. Frangou, S. Chang, C.-J. Chiu, W.-C. Liu, H.-C. Sun, I.-W. Liu, S.-I. et.al.
Publication Name: Am. J. Clin. Nutr.
Publication Details: Volume 95; Pages 420 – 427.
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)
Recent reports have shown that lower n-3 PUFAs may be associated with depression and dementia. Lower EPA (20:5n3), DHA (22:6n3), and total n3 PUFA concentrations have been found in people with depression. Negative associations between n-3 PUFA concentrations and the risks of cognitive dysfunction or dementia have been repeatedly reported. Higher n6 PUFA concentrations have been found in people with dementia, and higher plasma concentrations of AA (20:4n6) and SFAs, and lower n6 PUFA concentrations have been reported to be inversely related to cognitive decline. In a sample of older people with previous major depression, the following hypotheses were tested 1) total n3 PUFA concentrations in erythrocyte membranes would be positively associated with cognitive function and 2) associations with cognition may be more sensitive for erythrocyte concentrations than for plasma concentrations. A secondary aim was to explore the specificity of this association with respect to particular cognitive test results. Erythrocyte membrane EPA, DPA, and total n3 PUFA concentrations were positively and AA/EPA ratios were negatively associated with global cognitive function in older people with previous major depression after adjustment for age and sex, however, the associations were not significant after adjustment for education. No associations were found for plasma n3 PUFA concentrations. In secondary analyses, positive associations were found for erythrocyte ALA and n3 PUFAs concentrations with immediate verbal memory, which was robust to all adjustments, although only observed in participants with recurrent depression. Associations with cognitive function were found for erythrocyte membrane n3 fatty acid concentrations but not plasma concentrations. Lower plasma ALA concentrations have been reported in dementia and may have distinct biological actions that modulate depression and cognition. ALA deficiency may perturb the composition and physicochemical properties of brain cell membranes, neurons, oligodendrocytes, and astrocytes, which results in neurosensory and behavioral upset. In humans, higher ALA intake has been found to be related to lower plasma inflammatory biomarkers. Because inflammatory process are implicated in depression and cognitive impairment or dementia, the findings that immediate verbal recall is specifically associated with ALA and total n23 PUFA concentrations may be relevant. The positive associations between erythrocyte ALA or total n-3 PUFA concentrations and immediate recall were observed only in participants with recurrent depression so that a previous course may play a more important role than current symptoms. In conclusion, these findings suggest that erythrocyte total n3 PUFA concentrations are positively associated with cognitive function, particularly immediate recall, in older people with previous major depression. Lower concentrations of n3 PUFAs or ALA in erythrocyte membranes may be good predictors of cognitive impairment in this specific group. Further prospective studies are needed to investigate these associations and possible underlying mechanisms and to evaluate the value of n3 PUFA supplementation in people with late-life depression. (Editors comments)
Recent reports have shown that lower n-3 PUFAs may be associated with depression and dementia. Lower EPA (20:5n3), DHA (22:6n3), and total n3 PUFA concentrations have been found in people with depression. Negative associations between n-3 PUFA concentrations and the risks of cognitive dysfunction or dementia have been repeatedly reported. Higher n6 PUFA concentrations have been found in people with dementia, and higher plasma concentrations of AA (20:4n6) and SFAs, and lower n6 PUFA concentrations have been reported to be inversely related to cognitive decline. In a sample of older people with previous major depression, the following hypotheses were tested 1) total n3 PUFA concentrations in erythrocyte membranes would be positively associated with cognitive function and 2) associations with cognition may be more sensitive for erythrocyte concentrations than for plasma concentrations. A secondary aim was to explore the specificity of this association with respect to particular cognitive test results. Erythrocyte membrane EPA, DPA, and total n3 PUFA concentrations were positively and AA/EPA ratios were negatively associated with global cognitive function in older people with previous major depression after adjustment for age and sex, however, the associations were not significant after adjustment for education. No associations were found for plasma n3 PUFA concentrations. In secondary analyses, positive associations were found for erythrocyte ALA and n3 PUFAs concentrations with immediate verbal memory, which was robust to all adjustments, although only observed in participants with recurrent depression. Associations with cognitive function were found for erythrocyte membrane n3 fatty acid concentrations but not plasma concentrations. Lower plasma ALA concentrations have been reported in dementia and may have distinct biological actions that modulate depression and cognition. ALA deficiency may perturb the composition and physicochemical properties of brain cell membranes, neurons, oligodendrocytes, and astrocytes, which results in neurosensory and behavioral upset. In humans, higher ALA intake has been found to be related to lower plasma inflammatory biomarkers. Because inflammatory process are implicated in depression and cognitive impairment or dementia, the findings that immediate verbal recall is specifically associated with ALA and total n23 PUFA concentrations may be relevant. The positive associations between erythrocyte ALA or total n-3 PUFA concentrations and immediate recall were observed only in participants with recurrent depression so that a previous course may play a more important role than current symptoms. In conclusion, these findings suggest that erythrocyte total n3 PUFA concentrations are positively associated with cognitive function, particularly immediate recall, in older people with previous major depression. Lower concentrations of n3 PUFAs or ALA in erythrocyte membranes may be good predictors of cognitive impairment in this specific group. Further prospective studies are needed to investigate these associations and possible underlying mechanisms and to evaluate the value of n3 PUFA supplementation in people with late-life depression. (Editors comments)
