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.

backgroundTo explore the association of low-level lead exposure with all-cause mortality and cardiovascular disease (CVD) mortality among hypertensive patients.

methodsThis 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.

resultsDuring 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.

conclusionElevated 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.