The Mediating Role of Oxidative Stress in the Association Between Phthalate Exposure and Body Mass Index Among Adults: A Cross-Sectional Analysis Using NHANES Data

Background The study investigates the mediating role of oxidative stress in the relationship between phthalate exposure, measured via urinary Bisphenol A (BPA) levels, and Body Mass Index (BMI) in adults. Given the global prevalence of obesity and the widespread exposure to phthalates, understanding this relationship is critical. Methods: Data were derived from the National Health and Nutrition Examination Survey (NHANES), focusing on adult participants. Key variables included urinary BPA levels (independent variable), BMI (dependent variable), oxidative stress indicators (mediator), and covariates such as age, serum creatinine, poverty index, and race/ethnicity. Descriptive statistics summarized baseline characteristics, and mediation analysis quantified the direct, indirect, and total effects of phthalate exposure on BMI. Results: The study sample comprised 19,022 adults, with a nearly equal distribution of males and females. The median BMI and urinary BPA levels differed significantly by gender. Mediation analysis revealed that oxidative stress mediated approximately 19% of the total effect of phthalate exposure on BMI. The Average Causal Mediation Effect (ACME) was − 0.000976 (95% CI: -0.001147 to 0.001, p < 0.001), and the Average Direct Effect (ADE) was − 0.004155 (95% CI: -0.008239 to 0.001, p = 0.016). The total effect was − 0.005132 (95% CI: -0.008997 to 0.001, p = 0.004). Conclusions: This study highlights the significant role of oxidative stress in mediating the relationship between phthalate exposure and BMI. The findings suggest that strategies to reduce oxidative stress could mitigate the obesogenic effects of phthalates, underscoring the need for regulatory policies to limit phthalate exposure and public health interventions targeting oxidative stress. Future research should explore longitudinal data and a broader range of phthalate exposures to further elucidate these relationships.