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Postmortem Studies Suggest Moderate Consumption of Seafood Associated with Higher Brain Levels of Mercury but Lesser Alzheimer Disease Neuropathology

February 02, 2016 A cross-sectional analysis of postmortem findings of 286 participants in the Rush Memory and Aging Project (MAP)1 suggested that moderate consumption of seafood (i.e., 1 or more meals per week) was associated with lesser Alzheimer disease neuropathology, despite higher levels of mercury in the brain in these individuals. The study included analyses of deceased participants in the Memory and Aging Project clinical neuropathological cohort study for the years 2004-2013. Average age at death was 90 years and 67% of participants were female. Seafood intake was assessed by a food frequency questionnaire at an average of 4.5 years before death.

Brain mercury levels were positively correlated with the number of seafood meals consumed per week. In models adjusted for age, sex, education, and total energy intake, seafood consumption (i.e., 1 or more meals per week) was significantly correlated with less Alzheimer disease pathology (e.g., lower density of neuritic plaques, less severe and widespread neurofibrillary tangles, and lower neuropathologically defined Alzheimer disease); however, it is worth noting these findings were only observed in apolipoprotein E (APOE ε4) carriers, a gene variant associated with an increased risk of developing Alzheimer disease. These individuals would be more likely to have evidence of neuropathologic changes associated with Alzheimer risk than noncarriers.  The authors posit that “insufficient statistical power may have prevented detection of small correlations of n-3 fatty acids on neuropathology in APOE ε4 noncarriers.” Further, there was no statistically significant correlation between fish oil supplementation and any marker of neuropathology studied. Although seafood consumption was correlated with higher brain levels of mercury, the higher mercury levels were not significantly correlated with increased levels of brain neuropathology in APOE ε4 carriers.

In an accompanying editorial,2 Kröger and Laforce state, “…patients and their families may be hopeful that interventions such as seafood consumption may help reduce clinical manifestations of Alzheimer disease or dementia, and the [MAP study] provides reassurance that seafood contamination with mercury is not related to increased brain pathology.”

References

  1. Morris MC, Brockman J, Schneider JA, et al. Association of Seafood Consumption, Brain Mercury Level, and APOEε4 Status With Brain Neuropathology in Older Adults. JAMA 2016;315(5):489-97.
  2. Kröger E, Laforce Jr R. Fish Consumption, Brain Mercury, and Neuropathology in Patients With Alzheimer Disease and Dementia. JAMA 2016;315(5):465-6.

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