Association between mixed exposure of phthalates and cognitive function among the U.S. elderly from NHANES 2011–2014: Three statistical models

Abstract

BackgroundStudies on the relationship between phthalate exposure and cognition in adults are sparse and inconsistent. These studies only assessed their association of single phthalates for one-time and the tools for assessing cognitive function were different. ObjectiveWe aimed to examine the association between mixed phthalates and cognition in the U.S elderly using three statistical models. MethodsThe generalized linear (GLM), weighted quantile sum (WQS), and Bayesian kernel machine regression (BKMR) models were used to evaluate the associations between mixed phthalates and the standardized z-scores of four cognitive tests [Immediate Recall test (IRT), Delayed Recall test (DRT), Animal Fluency test (AFT), and Digit Symbol Substitution test (DSST)] in participants aged over 60 years from NHANES 2011–2014. Results835 individuals were included and the median raw scores of IRT, DRT, AFT, and DSST were 19 (IQR: 16–23), 6 (IQR: 5–8), 16 (IQR: 13–20), 46 (IQR: 35–59). In adjusted GLM, negative associations were observed between MECPP, MnBP, MCOP, MCPP, and the IRT z-scores; MCPP, MBzP, and the DRT z-scores. Positive relationships were found between MCOP, MCPP, and the AFT z-scores; MCPP and the DSST z-scores. The WQS index was associated with the IRT z-scores (β(95%CI): −0.069(−0.118, −0.020)), where MCPP weighted the highest. In the BKMR, negative overall trends between the mixture and the IRT, DRT z-scores were observed when the mixture was at 40th to 65th percentile, 65th percentile or above it, respectively, where MnBP and MBzP drove the main effect of the mixture. ConclusionThis study is an academic exploration of the association between phthalates exposure and cognitive function, suggesting that exposure to phthalates might be associated with bad performance in IRT and DRT in the U.S. elderly.