Association between polycyclic aromatic hydrocarbon exposure and cognitive performance in older adults: a cross-sectional study from NHANES 2011-2014

Background : polycyclic aromatic hydrocarbons (PAHs) are classified as neurotoxins, but the relationship between exposure to PAHs and cognition in adults is unclear, and their non-linear and mixed exposure association hasn't been explored. Objective : to evaluate the non-linear and joint association between co-exposure to PAHs and multiple cognitive tests in U.S. older people. Methods : restricted cubic spline (RCS) and Bayesian kernel machine regression (BKMR) were conducted to evaluate the non-linear and mixed exposure association, based on the cross-sectional data from NHANES 2011-2014: 772 participants over 60 years old, 4 cognitive test scores, including the Immediate Recall Test (IRT), Delayed Recall Test (DRT), Animal Fluency Test (AFT), and Digit Symbol Substitution test (DSST), and 5 urinary PAH metabolites. Results : a V-shaped nonlinear relationship was found between 3-hydroxyfluorene (3-FLUO), 2-hydroxyfluorene (2-FLUO), and DRT. Negative trends between mixed PAH exposure and IRT, DRT, and DSST scores were observed. 2-FLUO contributed the most to the negative association of multiple PAHs with IRT and DRT scores and 2-hydroxynaphthalene (2-NAP) played the most important role in the decreasing relationship between mixed PAH exposure and DSST scores. Conclusion : our study suggested that PAH exposure in the U.S. elderly might be related to their poor performances in IRT, DRT and DSST. Further prospective studies are needed to validate the association. Human exposure to PAHs originates from a wide range of sources. Our study found negative trends between mixed PAHs exposure and IRT, DRT, and DSST scores, suggesting that exposure to multiple PAHs is a risk factor for cognition in older adults.