This project contains code used for contributions to a class project (Adv. Analytic Methods in EHS).
Title: Per- and polyfluoroalkyl substances and body mass index: a mixtures approach using data from the National Health and Nutrition Examination Survey (NHANES) 2015-2016
Background: Per- and polyfluoroalkyl substances (PFAS) constitute a group of thousands of human-made, persistent compounds that have been used commercially and industrially for over sixty years. Exposure to PFAS chemicals is associated with increased risk of liver damage, higher cholesterol, thyroid disease, and decreased birth weight. The endocrine disrupting properties of PFASs may interfere with body weight regulation. This study investigates the association between serum concentrations of ten PFAS analytes and BMI using the most recent NHANES dataset (2015-2016).
Methods: We use a mixtures approach to reduce dimensionality (principal components analysis), test for nonlinear dose-response curves using generalized additive models, and apply quantile regression to determine the effects of PFAS on the distribution tails of BMI.
Results: Overall, we found null and negative associations between exposure to PFAS chemical serum concentrations and BMI in a general US sample. We identified signals of potential nonlinear effects for 2-(N-methylperfluoroctanesulfonamido) acetic acid, perfluoroundecanoate, n-perluorooctanoate, perfluorooctane sulfonate,and principal component 1, although more observations are needed at higher PFAS concentration ranges to tighten confidence intervals. We reduced the mixture of ten PFAS chemicals to three components using Principal Components Analysis, accounting for 63.1 percent of the variance, and found slight negative associations with BMI for the first and third principal component. In addition, we found that exposure to PFAS chemicals had statistically significant inverse associations trending towards a lower BMI particularly in the upper distribution percentiles.
Conclusions: More research is needed to determine the effects of both individual chemicals and exposure to a mixture of PFAS compounds, using appropriate mixtures methods, in populations chronically exposed to a higher distribution of PFAS chemicals. Additionally, more research targeting susceptible populations, such as children, is needed to inform public health standards.