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 (∑As) in urine was associated with limited fine motor functioning and processing speed. A 10% increase in ∑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 ∑As was associated with a .15 (95% CI -.29, .00) decrease on the Wechsler Adult Intelligence Scale-Fourth Edition Coding Subtest. ∑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.