In a study of older adults, researchers did not find a definitive association between blood mercury levels, which can become elevated with fish consumption, and adverse neurobehavioral effects, according to a study in the April 20 issue of JAMA.
Mercury can be found throughout the environment, and enters the air during fossil-fuel combustion, mining, smelting, and solid-waste incineration, according to background information in the article. It is converted to methylmercury by microorganisms, enters the food chain, and accumulates in predatory fish. Consumption of certain fish is the primary source of methylmercury exposure in the general population. Methylmercury distributes rapidly throughout the body and easily crosses the blood-brain barrier into the brain, where it may become trapped.
Recent regulations for mercury emissions, the increasing trend in fish-consumption advisories, clinical studies, and heightened media attention have led to the emergence of mercury as a leading public health concern. Fish consumption is frequently recommended for older adults due to its high omega-3 fatty acid content, well-documented cardiovascular benefits, and, more recently, its possible protective association with Alzheimer disease. Since the aging nervous system is more sensitive to neurotoxicants, there is reason for concern about mercury contamination in fish.
Megan Weil, M.H.S., of the Johns Hopkins Bloomberg School of Public Health, Baltimore and colleagues conducted a study to examine associations between mercury exposure and neurobehavioral outcomes in a representative sample of older adults in the United States. The research included 474 randomly selected participants in the Baltimore Memory Study, a longitudinal study of cognitive decline involving 1,140 Baltimore residents aged 50 to 70 years. Total mercury in whole blood samples was measured and the researchers used multiple linear regression to examine its associations with scores from 12 neurobehavioral tests. First-visit data were obtained in 2001-2002. Participants also completed a food frequency questionnaire to determine fish consumption levels