Association of low-level lead exposure with all-cause and cardiovascular disease mortality in US adults with hypertension: evidence from the National Health and Nutrition Examination Survey 2003–2010

Abstract Background To explore the association of low-level lead exposure with all-cause mortality and cardiovascular disease (CVD) mortality among hypertensive patients. Methods This cohort study enrolled 6453 adults with hypertension from the National Health and Nutrition Examination Survey 2003–2010 and followed mortality information through December 31, 2019. The baseline population were divided into four groups based on quartiles of blood lead levels (Q1: < 1.2 μg/dL, Q2: 1.2–1.6 μg/dL, Q3: 1.7–2.4 μg/dL, Q4: 2.5–4.9 μg/dL). The correlation of blood lead levels to mortality was investigated by Kaplan–Meier survival curves, restricted cubic spline (RCS), proportional hazard regression model, and subgroup analysis. Results During a median follow-up period of 136 (interquartile range 113, 164) months, a total of 1943 (30.1%) deaths were documented, among which 553 (28.5%) were due to CVD. Blood lead showed a linear dose–response relationship with all-cause and CVD mortality. After adequate adjusting for confounders, the risk of all-cause death rose by 23% for each unit increase in continuous variable blood lead (hazard ratio (HR): 1.23; 95% confidence interval (CI):1.16–1.30). When blood lead was a quartile group variable, participants in the Q 4 group had a 73% higher risk of death than those in the Q 1 group (HR:1.73; 95% CI: 1.43–2.10; P for trend < 0.001). The association for CVD mortality was analogous. The concordant results were achieved in the subgroup analysis. Conclusion Elevated blood lead levels were strongly associated with an increased all-cause and CVD mortality in adults with hypertension, even at the reference range of blood lead