Abstract
Cognitive function frequently declines with older age, independently of the development of neurodegenerative diseases, and few interventions are known to counter this decline. Exposure to neurotoxic metals may contribute to this decline in cognitive function in older adults. Using the National Health and Nutrition Examination Survey (NHANES) data, the performance of 3042 adults aged 60 years and older on three cognitive tests for immediate, delayed, and working memory were examined in relation to blood concentrations of seven metals and metalloids and urinary concentrations of nineteen metals and metabolites. Using linear regression models, associations between cognitive tests and logarithms of metal exposures were adjusted for age, sex, ethnicity, education level, depression, diabetes, alcohol consumption, and cigarette use. Increased selenium was strongly associated with better performance on all three cognitive tests. Cadmium and lead were negatively associated with performance on all three cognitive tests. Some urinary metabolites of arsenic, urinary lead, cadmium, and tungsten were significantly associated with poor performance on some tests. In older adults, higher selenium levels were strongly associated with better cognitive performance.
Highlights
Cognitive function often declines with age, even in people without neurodegenerative diseases, the rate of decline shows significant heterogeneity among individuals
Because several metals are known to reduce learning and memory, we explored National Health and Nutrition Examination Survey (NHANES) data to examine whether metal exposures were important factors influencing cognitive function in older adults
We examined cross-sectional associations to understand which metals or metabolites have associations with cognitive function tests relating to immediate learning and recall, delayed recall, and working memory in older adults using data from the NHANES
Summary
Cognitive function often declines with age, even in people without neurodegenerative diseases, the rate of decline shows significant heterogeneity among individuals. Exposures to lead [1–3], cadmium [4], methylmercury [5,6], and arsenic [7–9] are known to reduce cognitive function and cause neurobehavioral effects in children. Lead concentrations as low of 5 μg/dL had significant adverse effects on attention, arithmetic, and reasoning scores among children aged 6–16 years in a crosssectional study [2]. From a longitudinal study, it was found that the rate of decline in IQ at 3 and 5 years of age was steeper at lower than at higher concentrations of postnatal lead exposures [3]. While prenatal cadmium exposures have not been shown to be significantly associated with children’s cognitive performance at ages 1–8 years in prospective pregnancy and birth cohorts, negative effects on cognitive function are suggested in animal models [4,10]. Arsenic exposures in children aged 6–8 years have been linked to reduced cognitive performance even after adjusting for the effects of lead [7,8].
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