The National Health and Nutrition Examination Survey, administered by the National Center for Health Statistics, is a comprehensive program aimed at assessing the health and nutritional status of both adults and children in the United States. Data from this project have been updated biennially since 1999. The survey utilizes a complex multi-stage probability sampling strategy to select 5000 representative populations from different regions throughout the country. These individuals are then surveyed on a variety of demographic, socioeconomic, dietary, and health-related issues before undergoing health measurements and biological sample collection at mobile testing centers. All participation in NHANES is voluntary, with procedures being ethically reviewed (Continuation of Protocol #2011-17) and informed consent being obtained from all participants. For our study, we selected participants from two cycles spanning 2015-2018 who met specific inclusion criteria: they were over 20 years old; provided complete PFAS and uric acid measurements; and had no missing key covariate information. S1 presents a flow chart detailing the selection process for these participants.
