Environmental mercury exposure and neurobehavioral function in older adults

Problem. Mercury is ubiquitous in the environment; exposure to methylmercury, a highly toxic form of mercury, poses a risk to susceptible populations, mainly through fish consumption. The neurological effects of mercury have been studied in children, women of child-bearing age, and highly exposed populations. However, older adults in the U.S. have not been studied despite the increasing sensitivity of their central nervous system. Further, this is the fastest growing population and the one most at risk for cognitive dysfunction.; Methods. Using first visit data and blood samples from the longitudinal Baltimore Memory Study, this cross-sectional study analyzed blood mercury level and neurobehavioral function in conjunction with two factors potentially involved in mercury's mechanism of toxicity (metallothionein and oxidized low-density lipoprotein). Multiple linear regression was used to model these variables and the relations between them in 474 Baltimore city residents aged 50-70 years.; Results. The median mercury level was 2.1 mug/L (range: 0-16 mug/L). After adjustment for covariates, persons in the highest quartile of fish consumption had median blood mercury levels that were 1.82 times higher than those in the lowest quartile. Higher assets, education, and being white were also all significantly associated with higher mercury levels. Modeling neurobehavioral test scores showed increasing blood mercury was associated with worse performance on a test of visual memory, after adjustment for covariates. However, increasing blood mercury levels were also associated with better performance on a test of manual dexterity. Neither metallothionein, nor oxidized low-density lipoprotein showed associations with mercury or cognitive function, looking at each as a both predictor and an effect modifier.; Conclusions. Overall, the data do not provide strong evidence that blood mercury levels are associated with worse neurobehavioral performance in this population of older urban adults. Pending future studies of mercury and cognitive function, public health scientists and organizations should target messages about mercury and fish consumption to whites in higher socioeconomic strata.