Fish intake and the long-chain omega-3 polyunsaturated fatty acids (PUFAs) in fish have been suggested to lower the risk of cognitive decline. We assessed whether serum long-chain omega-3 PUFAs eicosapentaenoic acid (EPA), docosapentaenoic acid (DPA) and docosahexaenoic acid (DHA) are associated with performance on neuropsychological tests in an older population and whether exposure to methylmercury, mainly from fish, or apolipoprotein-E4 (Apo-E4) phenotype can modify the associations.
A total of 768 participants from the population-based Kuopio Ischaemic Heart Disease Risk Factor Study were included. Cognitive function was measured using five neuropsychological tests: the Trail Making Test, the Verbal Fluency Test, the Selective Reminding Test, the Visual Reproduction Test and the Mini Mental State Exam. Multivariate-adjusted analysis of covariance and linear regression were used to analyze the cross-sectional associations.
We found statistically significant associations between serum EPA+DPA+DHA and better performance in the Trail Making Test and the Verbal Fluency Test. The individual associations with EPA and DHA were similar with the findings with EPA+DPA+DHA, although the associations with DHA were stronger. No associations were observed with serum DPA. Pubic hair mercury content was associated only with a worse performance in the Trail Making Test, and mercury had only little impact on the associations between the serum PUFAs and cognitive performance. Apo-E4 phenotype did not modify the associations with PUFAs or mercury.
Higher serum long-chain omega-3 PUFA concentrations were associated with better performance on neuropsychological tests of frontal lobe functioning in older men and women. Mercury exposure or Apo-E4 phenotype had little impact on cognitive performance.