The predictive value of multiple urinary metals in evaluating death risk in asthmatic individuals: a prospective cohort study

There is very limited epidemiological research available to verify how metal exposure impacts the prognosis of individuals with asthma. This study aimed to investigate the value of multiple urinary metals in assessing the prognosis of asthma patients by utilizing data from NHANES and constructing the predictive models. This study employed Cox regression models, survival 3D interaction plots, and survival curves to examine the associations between urinary metals and the outcomes among asthmatic patients. This study also employed LASSO regression to find key variables for the prediction model and then employed time-dependent receiver operating characteristic (ROC) curves and Shapley additive explanations (SHAP) models to evaluate how well the prediction model performed and its usefulness. The Cox regression models, survival 3D interaction plots, and survival curves all verified that, after controlling for confounders, the higher concentrations of urinary cadmium (HR: 1.76, 95% CI: 1.08–2.87) and cobalt (HR: 1.27, 95% CI: 1.06–1.52), the lower the survival rate and the higher the risk of death for asthma patients. However, no significant associations were observed between the other seven urinary metals (barium, cesium, molybdenum, manganese, lead, tin, and tungsten) and the prognosis of asthma patients. According to the LASSO regression and SHAP model, the most significant indicators predicting mortality in individuals with asthma were age, cadmium, cobalt, diabetes, cancer, other chronic airway diseases, and cardiovascular disease. The combination of these seven indicators exhibited superior performance when predicting the 1-year (AUC: 0.82), 5-year (AUC: 0.86), and 9-year (AUC: 0.82) death risk of asthma populations. This study revealed that when the urinary cadmium concentration of asthma patients exceeded 0.21 µg/L or the urinary cobalt concentration exceeded 0.98 µg/L, urinary cadmium and cobalt concentrations were positively associated with mortality among asthma patients. Urinary cadmium and cobalt, when combined with other markers, can serve as effective and practical instruments for predicting adverse outcomes in asthmatic populations.