Abstract
BACKGROUND: In the USA, racial disparities in blood pressure have persisted, with Black people experiencing a greater risk of hypertension compared with White people. While disparities in lead exposure may be related to some of this disparity, little is known about the mediating role of lead in racial disparities in blood pressure. METHODS: We used national-level, cross-sectional data of non-institutionalized US adults aged ≥20 years from the National Health and Nutrition Examination Survey (NHANES): NHANES-III (1988-1994) (n = 10 570) and NHANES 2017-2020 (n = 4536). We examined the extent to which racial disparities in blood pressure were mediated by disparities in blood lead levels between these two NHANES cycles by using causal mediation analysis. We estimated natural direct and indirect effects, and considered potential interaction between race and blood lead levels by using four-way decomposition. RESULTS: In NHANES-III, the Black participants would have a 5.74-mmHg (95% confidence interval: 4.94, 6.54) higher mean systolic blood pressure compared with White participants if all adjusted covariates were held equal to that of the White population; 10% of this disparity was mediated by differences in blood lead levels between Black and White participants. Similar trends were observed for hypertension. In NHANES 2017-2020, similar overall trends were observed. However, the proportion of racial disparities mediated by differences in blood lead levels between Black and White individuals reduced from 10% to 5%. CONCLUSION: These findings suggest that racial differences in lead exposure may be related to racial disparities in blood pressure, but the mediating role of blood lead levels has decreased since the 1980s.