Lower omega-3 fatty acid intake and status are associated with poorer cognitive function in older age: A comparison of individuals with and without cognitive impairment and Alzheimer's disease.

Objective: Various strands of evidence suggest that low intake of omega-3 fatty acids increases risk of cognitive decline and dementia. The present study investigated differences in dietary intake and blood plasma content of eicosapentaenoic acid (EPA; 20:5n-3) and docosahexaenoic acid (DHA; 22:6n-3) in individuals with cognitive impairment no dementia (CIND), individuals with Alzheimer's disease (AD), and healthy volunteers (HV).

Methods: A total of 135 individuals aged between 55 and 91 years (19 AD, 55 CIND, and 61 HV) were assessed predominantly within a hospital setting.

Results: Compared with age and sex-matched HV, individuals with AD or CIND performed poorly on a majority of tests of cognitive function. Impairment was greatest for delayed and verbal recognition memory. CIND individuals were less impaired than AD individuals. Omega-3 intake and the percentage of EPA and DHA in plasma phosphatidylcholine (PC) showed a similar pattern (AD < HV, with intermediate scores for CIND). Across the whole sample, and after controlling for age, years of education, level of socio-economic deprivation, and gender, omega-3 intake, plasma PC DHA, and plasma PC EPA were all significant positive predictors of memory functioning.

Conclusions: These results are consistent with the possibility that omega-3 fatty acid nutrition has an impact on cognitive decline, but could equally be explained by dietary changes that occurred after onset of cognitive decline. It is also possible that the results could be explained by unknown confounding factors.