Allostatic Load as a Modifier of Associations Between Metals and Blood Pressure

BACKGROUND AND AIM: Disadvantaged populations are often co-exposed to high levels of metals and psychological stressors. While limited research suggests that stress may increase susceptibility to lead cardiotoxicity, the influence of stress on other metals remains unexplored. We examined whether allostatic load (AL), a measure of chronic stress, modifies associations between metals (cadmium, mercury, arsenic, antimony, cesium, cobalt, molybdenum, thallium, tungsten, uranium, or lead) and blood pressure (BP). METHODS: We analyzed cross-sectional data on 11 blood and urinary metal biomarkers and systolic and diastolic BP in 5,022 adults (20+ years) participating in NHANES 2003-2010 using linear regression models. We assessed whether associations were modified by AL using interaction terms and stratified analyses. Because there is no scientific consensus on how to measure AL, we compared four different approaches to dichotomize participants into high and low AL based on seven stress biomarkers. Final models for each metal were adjusted for age, sex, race/ethnicity, BMI, education level, serum cotinine, urinary creatinine (to account for urinary dilution), and other confounding metals (e.g., lead). RESULTS: For diastolic BP, we observed no significant interactions between any metals and AL, but stratified analyses indicated that blood lead and urinary cobalt were significantly associated with higher BP in the high AL group only. These results were robust to the method used to define AL. For systolic BP, we observed the opposite trend: blood lead and urinary cobalt were associated with higher BP in the low AL group but not the high AL group, though results varied by AL definition. CONCLUSIONS: AL may modify the association between certain metals and BP in adults. As results may differ by method used to define AL, future research should use multiple approaches to operationalize AL until consensus is reached on the most appropriate definition. KEYWORDS: Metals, Stress, Blood Pressure, Allostatic Load