Association Between Long-Term Dietary Exposure to Organophosphate Pesticides and Neurocognition: The Multi-Ethnic Study of Atherosclerosis (MESA)

Background: Organophosphate pesticides (OPs) are the primary form of insect control in American agriculture. For non-occupationally exposed individuals, the primary source of OP exposure is thought to be through diet, via ingestion of foods to which OPs are applied. OP exposure has been associated with decrements in neurocognitive performance in occupationally exposed adults and in children in the general population.

Methods: We estimated long-term dietary OP exposure for 3,613 adults in the MESA cohort by combining information on self-reported dietary intake via food frequency questionnaire with national OP residue data. We evaluated the relationship between exposure and neurocognition, assessed by the Forwards Digit Span Test (FDST), the Backwards Digit Span Test, the Digit Symbol Coding Test, and the Cognitive Abilities Screening Instrument. Models were adjusted for age, sex, race/ethnicity, metropolitan area, education, income and neighborhood factors related to food availability. We also tested whether organic food consumption modified these associations.

Results: Greater dietary OP exposure was associated with lower scores on the FDST, but not the other three tests of neurocognition. An interquartile difference in exposure of 4 ng/kg-day was associated with a -0.16 units difference on the FDST (CI: -0.29, -0.01; p = 0.04), approximately the same difference we observe per +5 years of age in this cohort. Discussion: Long-term dietary OP exposure was associated with decreased performance in the phonological loop component of auditory working memory, the domain measured by the FDST. OP exposure was not associated with three other tests, which measure the visuospatial component of working memory, speed of mental processing, and more general cognitive abilities. These results suggest there may be a benefit to minimizing dietary OP exposure, although the observed differences were small and variable across multiple neurocognitive domains.