Cognition and Per- and Polyfluoroalkyl Substances (PFAS): Older Adult sample from the NHINES trial

Per- and polyfluoroalkyl substances (PFAS) are synthetic fluorinated chemicals with both hydrophobic and lipophobic properties, due to their structure consisting of a fluorocarbon backbone and strong covalent carbon-carbon and carbon-fluorine bonds. With such unique properties, PFAS are considerably persistent and bioaccumulative, owing to the concentrations at which they are found in the environment as well as the human body. Though deemed persistent, the properties of PFAS were considered useful when they were introduced into manufacturing of industrial and consumer products, such as firefighting foams and nonstick pans. The persistence of PFAS allowed for these chemicals to become prevalent in food, water, and air. With such variable ways of transport, PFAS were able to be ingested by humans. The goal of this study is to determine whether higher concentrations of PFAS have an effect on the cognition of adults ranging from 60 to 80 years old. Data was obtained from the National Health and Nutrition Examination Survey (NHANES)  for the years of 2013-2014. Measurements from nineteen types of PFAS were used and data from four cognitive tests were obtained (Park, 2021). Animal fluency is a measurement of language and executive function, often applicable in assessing people with Alzheimer’s Disease as well as other neurological disorders. The CERAD-WL test assesses the ability of learning and recalling verbal information. The Digit Symbol Substitution test (DSST) measures human cognitive learning, specifically for everyday tasks. The fourth cognitive test considered was the savings score, calculated from the scores of the delayed trial and the third trial of the DSST. Z-scores were calculated in SPSS for all four cognitive tests, and an average of all tests was calculated to make a composite z-score. Preliminary results suggest that perfluorononanoic acid (PFNA), perfluorodecanoic acid (PFDA), and hexafluoropropylene oxide-dimer acid (HFPO-DA), have significant relationship to cognition (animal fluency; r = -.12, -.09, .12; and p = .01, .05, .01, respectively). Interestingly directionality is mixed, and prior literature confirms it is sometimes unclear if PFAS exposure has a uniform cognitive cost or if it might sometimes be neuro-protective. Caution in interpretation is called for given multiple statistical tests and escalating error rate with such exploration. Covariates such as sex may be important for follow-up analyses given the significant relationship with total PFAS (r = -.58; p = .01) Ongoing work will focus on investigating the relationship between PFAS concentrations and cognition, via multiple regression with inclusion of covariates such as economic status, specifically regarding animal fluency.