Association between blood heavy metal levels and COPD risk: a cross-sectional study based on NHANES data.

Objective: Heavy metals such as cadmium (Cd), lead (Pb), mercury (Hg), selenium (Se), and manganese (Mn) are commonly found in the environment and could increase the risk of COPD, potentially through key biological mechanisms such as oxidative stress and inflammation. Nonetheless, evidence on the association between exposure to these metals and COPD remains limited and inconclusive. This study aims to evaluate the potential association between blood levels of Cd, Pb, Hg, Se, and Mn and the likelihood of developing COPD.

Methods: This cross-sectional analysis utilized data from 7,458 individuals from the NHANES. COPD status was determined based on self-reported physician diagnoses obtained from questionnaires. Multivariate logistic regression models were applied to examine the association between blood heavy metal levels and the risk of COPD. Subgroup analyses were conducted to explore potential differences in these associations across various population groups. Additionally, smoothing curve analysis was used to investigate nonlinear relationships between heavy metal concentrations and COPD. The receiver operating characteristic (ROC) curve analysis was employed to assess the predictive value of blood metal levels for COPD risk.

Results: Blood levels of Cd and Pb were markedly elevated in COPD patients compared to those without the condition. Even after controlling for multiple confounders, higher blood levels of Cd and Pb were found to be significantly associated with a greater risk of developing COPD [odds ratio (OR) = 1.27, 95% confidence interval (CI): 1.13-1.44 and OR = 1.69, CI: 1.13-1.50, respectively; both  < 0.001]. The smoothing curve analysis demonstrated a nonlinear positive relationship between Cd and Mn levels and the risk of COPD. ROC curve analysis showed that Pb had the highest Area Under the Curve (AUC) value of 0.6744, suggesting different levels of sensitivity and specificity for these heavy metals in predicting COPD risk.

Conclusion: This study highlights that a significant association was observed between blood levels of Cd and Pb and the likelihood of developing COPD, with a significant trend across exposure quartiles. Moreover, the data suggest a nonlinear positive correlation between exposure to Cd and Mn and COPD. ROC analysis further revealed differential sensitivity and specificity among the five heavy metals in predicting COPD risk.