Low-level inorganic arsenic exposure and neuropsychological functioning in American Indian elders

Background: Inorganic arsenic at high and prolonged doses is highly neurotoxic. Few studies have evaluated whether long-term, low-level arsenic exposure is associated with neuropsychological functioning in adults. Objectives: To investigate the association between long-term, low-level inorganic arsenic exposure and neuropsychological functioning among American Indians aged 64-95. Methods: We assessed 928 participants in the Strong Heart Study by using data on arsenic species in urine samples collected at baseline (1989-1991) and results of standardized tests of global cognition, executive functioning, verbal learning and memory, fine motor functioning, and speed of mental processing administered during comprehensive follow-up evaluations in 2009-2013. We calculated the difference in neuropsychological functioning for a 10% increase in urinary arsenic with adjustment for sex, age, education, and study site. Results: The sum of inorganic and methylated arsenic species (Sigma As) in urine was associated with limited fine motor functioning and processing speed. A 10% increase in Sigma As was associated with a.10 (95% CI -.20, -.01) decrease on the Finger Tapping Test for the dominant hand and a.13 decrease (95% CI -.21, -.04) for the non-dominant hand. Similarly, a 10% increase in Sigma As was associated with a.15 (95% CI -.29,.00) decrease on the Wechsler Adult Intelligence Scale-Fourth Edition Coding Subtest. Sigma As was not associated with other neuropsychological functions. Conclusions: Findings indicate an adverse association between increased urinary arsenic fine motor functioning and processing speed, but not with other neuropsychological functioning, among elderly American Indians.