Association between exposure to organophosphate esters and cognitive function in older adults in the United States: NHANES 2011-2014

Background Organophosphate esters (OPEs) are widely used as an alternative to the brominated flame retardant polybrominated diphenyl ethers. The effects of OPEs on the cognitive abilities of older adults remain unclear. Methods A cross-sectional study was conducted using data from the National Health and Nutrition Examination Survey 2011-2014. Cognitive function was assessed using the Consortium to Establish a Registry for Alzheimer's Disease (CERAD) word learning test, the CERAD word recall test, the Animal Fluency Test (AFT), and the Digit Symbol Substitution Test (DSST). OPE metabolites with detection rates above 50% were included in the study. Weighted multiple linear regression, weighted quantile sum (WQS) regression, and Bayesian kernel machine regression (BKMR) models were used to examine the effects of individual and mixed exposures to OPE metabolites on cognitive function. Results A total of 762 older adults were included. The weighted linear regression model revealed a positive association between Ln DPHP, Ln BDCPP, and Ln BCPP and the DSST score, while a negative association was observed between Ln DBUP and the DSST score. In the positive WQS model, the index was correlated with DSST score (beta = 2.65, 95% CI: 0.40 similar to 4.90, P = 0.02), with DPHP having the highest weight. The results of BKMR analysis indicated a borderline statistical significance in the increase of DSST score when the mixture of OPEs is set to a specific 90th percentile compared to all mixture concentrations set to the median. Conclusions Overall exposure to OPE metabolites are associated with improved cognitive function in older adults in the United States. Further prospective studies with large sample sizes are needed to confirm these results.