Blood mercury levels and neurobehavioral function.

CONTEXT: Due to its cardiovascular benefits, fish consumption is widely encouraged among older Americans. However, this fast-growing population is at increased risk of cognitive impairment and may be particularly sensitive to methylmercury, a neurotoxicant found in fish.

OBJECTIVE: To describe associations of blood mercury levels with neurobehavioral test scores in an urban adult population.

DESIGN, SETTING, AND PARTICIPANTS: Cross-sectional analysis to determine the effect of mercury levels on neurobehavior in 474 randomly selected participants in the Baltimore Memory Study, a longitudinal study of cognitive decline involving 1140 Baltimore residents aged 50 to 70 years. We measured total mercury in whole blood samples and used multiple linear regression to examine its associations with neurobehavioral test scores. First-visit data were obtained in 2001-2002.

MAIN OUTCOME MEASURES: Twenty scores from 12 neurobehavioral tests.

RESULTS: The median blood mercury level was 2.1 microg/L (range, 0-16 microg/L). After adjustment for covariates, increasing blood mercury was associated with worse performance on Rey complex figure delayed recall, a test of visual memory (beta, -0.224; 95% confidence interval, -0.402 to -0.047). However, increasing blood mercury levels were associated with better performance on finger tapping, a test of manual dexterity (beta for dominant hand, 0.351; 95% confidence interval, 0.017-0.686).

CONCLUSION: 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.