Association between urinary phthalate metabolites and sarcopenia in US adults from NHANES 2011–2018

Phthalates, widely used as chemical additives, are often found as mixtures in the environment. However, the combined impact of phthalate exposure on sarcopenia remains unclear. This study aimed to investigate the relationships between phthalates and sarcopenia in adults. We analyzed data from 3,536 participants from the National Health and Nutrition Examination Survey (NHANES) conducted between 2011 and 2018.Multivariable logistic regression, restricted cubic splines (RCSs), weighted quantile sum regression (WQS), quantile-based g computation (qgcomp), and Bayesian kernel machine regression (BKMR) models were employed to assess the individual, nonlinear, and combined associations between phthalate metabolites and sarcopenia. In addition, subgroup analyses were performed to elucidate sex- and age-specific differences. Multivariable logistic regression revealed that MBP, MEP, and MiBP were positively associated with sarcopenia (P < 0.05) after adjusting for several covariates, including age, sex, race/ethnicity, education level, marital status, body mass index (BMI), smoking status, alcohol drinking, hypertension, diabetes, stroke, congestive heart failure, chronic kidney disease, physical activity, protein intake and energy intake. MBP exhibited a nonlinear relationship with sarcopenia in the RCS model. Furthermore, mixed phthalate metabolites were associated with a higher risk of sarcopenia in the WQS and qgcomp models. The BKMR model indicated an increasing trend in sarcopenia risk. Subgroup analyses showed stronger associations among individuals aged 20-40 years. BKMR analyses also revealed potential interaction effects between MCPP, MECPP, MBP, and MEP on sarcopenia risk. This study provides new evidence that co-exposure to phthalates might increase the risk of sarcopenia. Further research is needed to explore the causal relationship between phthalate metabolites and sarcopenia, as well as to elucidate the underlying mechanisms involved.