UC Berkeley

Background:Scientists and regulators have sought to understand whether and how physiologic dysregulation due tochronic stress exposure may enhance vulnerability to the adverse health effects of toxicant exposures. We conducted across-sectional study to determine whether allostatic load (AL), a composite measure of physiologic response tochronic exposure to stress, amplifies the effect of lead exposure on blood pressure among middle-aged adults.Methods:We analyzed associations between blood lead levels and blood pressure in a nationally representativesample of 8,194 U.S. adults (aged 40-65 years) participating in the National Health and Nutritional Examination Survey,1999--2008. Outcomes were elevated systolic (≥140 mm Hg) and diastolic (≥90 mm Hg) blood pressure. AL wasdefined as the aggregate score of seven components, reflecting dysregulation of the cardiovascular, inflammatory, andendocrine systems.Results:Logistic regression models showed a linear dose-response relationship for quintiles of blood lead and elevatedsystolic blood pressure in the high AL group (p = 0.03) but not the low AL group (p = 0.24). Similarly, the relationshipbetween lead exposure and elevated diastolic blood pressure was stronger among the high AL group than the low ALgroup. Within the high AL group, the fourth and fifth quintiles had significantly elevated odds of elevated bloodpressure compared to lowest quintile [OR = 1.92, (95% CI, 1.07, 3.47) and OR =2.28 (95% CI, 1.33, 3.91), respectively]. Inthe low AL group, none of the quintile effects were significantly different than the referent group although there wasevidence of a linear trend (p =0.03). The lead by AL interaction term was not statistically significant for either systolic ordiastolic blood pressure models.Conclusions:Results suggest that higher AL may amplify the adverse effects of lead on blood pressure. Futureresearch should assess the implications of cumulative exposures to environmental and social stressors for regulatory

decision-making