Environmental Pesticide Exposure and Cognition Among Adults 60 Years and Older in the United States

Purpose: Cognitive decline is an increasingly important public health issue among elderly adults that can lead to loss of memory, decreased ability to function, and numerous other health burdens. Pesticides are commonly manufactured and distributed chemicals that are frequently used for occupational farming and within households. Pesticide exposure has been examined as a possible risk factor for cognitive decline in the past; however, a complete understanding of this relationship remains unclear. This study examined the association between pesticide exposure and cognition, taking into consideration the potential influence of lifestyle factors and comorbidities. Methods: Based on the nationally representative, 2011 - 2014 National Health and Nutrition Examination Survey (NHANES), the study included 733 participants aged greater than or equal to 60 years who completed cognition tests and had available data on urinary concentrations of six pyrethroid, herbicide, and organophosphate pesticide metabolites. Linear regression models were applied to examine the associations between pesticide exposure and cognition, measured by global cognitive z-score. Results: After adjusting for demographic and other confounding factors, a higher level of para-Nitrophenol was marginally associated with lower global cognitive z-score (β = -0.0761, 95% CI [-0.24, 0.09], highest vs. lowest tertile); however, the association was not statistically significant. When stratified, the association of 4-fluoro-3-phenoxy-benzoic acid with lower global cognition score was primarily observed among former smokers in the 0-50% detectable level (β = -0.3633, 95% CI [-0.68, -0.04]) and among the participants with a poverty income ratio (PIR) < 1.85 in both the 0-50% (β = -0.6678, 95% CI [-1.25, -0.09]) and 50-100% detectable levels (β = -0.3196, 95% CI [-0.62, -0.02]). The interactions with smoking and PIR status were statistically significant (p < 0.05). Among females, a higher level of para-Nitrophenol and both the 0-50% and 50-100% detectable levels of 4-fluoro-3-phenoxy-benzoic acid were marginally associated with lower global cognition; however, neither of these associations were statistically significant. There were no clear associations for global cognition with other pesticide metabolites. Conclusions: Our findings suggest that higher para-Nitrophenol exposure may associate with poor cognitive function in older adults. 4-fluoro-3-phenoxy-benzoic acid may impair cognition among former smokers and those with a PIR < 1.85. Future studies are needed to confirm the findings and to further understand mechanisms between pesticide exposure and cognitive decline.