Trends in urine lead and associated mortality in US adults: NHANES 1999-2018

Objectives: This study aimed to describe the trends of urine lead among US adults aged >= 45 years and to explore its association with all-cause and disease-specific mortality. Methods: This study enrolled 9,669 participants from the National Health and Nutrition Examination Survey, 1999-2018. Trends in urine lead were described by logistic regression analysis using the survey cycle as a continuous variable. Cox proportional hazard regression analyses were used to quantify the association between urine lead and mortality. Results: There was an obvious decline in urine lead concentrations from 1.203 mu g/L (95% confidence interval [CI]: 1.083-1.322) in 1999-2000 to 0.478 mu g/L (95% CI: 0.433-0.523) in 2017-2018, and this decline was statistically significant (P < 0.001). Referring to the first tertile of urine lead concentrations, risk magnitude for all-cause mortality was significantly and linearly increased after adjustment (P = 0.026 and 0.020 for partially and fully adjusted models, respectively), and significance was attained for the comparison of the third vs. first tertile after full adjustment (hazard ratio [HR]: 1.17, 95% CI: 1.01 to 1.35). Treating urine lead continuously, the risk for all-cause mortality was statistically significant (HR: 1.18 and 1.19, 95% CI: 1.01 to 1.39 and 1.00 to 1.40 for partially and fully adjusted models). For cardiovascular disease-specific and cancer-specific mortality, there was no hint of statistical significance. Conclusions: Our findings indicated that urine lead exhibited a declining trend from 1999-2000 to 2017-2018 in US adults aged >= 45 years, and high urine lead was a significant and independent risk factor for all-cause mortality.