Allostatic load amplifies the effect of blood lead levels on elevated blood pressure among middle-aged U.S. adults: a cross-sectional study

Abstract

BackgroundScientists and regulators have sought to understand whether and how physiologic dysregulation due to chronic stress exposure may enhance vulnerability to the adverse health effects of toxicant exposures. We conducted a cross-sectional study to determine whether allostatic load (AL), a composite measure of physiologic response to chronic exposure to stress, amplifies the effect of lead exposure on blood pressure among middle-aged adults.MethodsWe analyzed associations between blood lead levels and blood pressure in a nationally representative sample 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 was defined as the aggregate score of seven components, reflecting dysregulation of the cardiovascular, inflammatory, and endocrine systems.ResultsLogistic regression models showed a linear dose-response relationship for quintiles of blood lead and elevated systolic blood pressure in the high AL group (p = 0.03) but not the low AL group (p = 0.24). Similarly, the relationship between lead exposure and elevated diastolic blood pressure was stronger among the high AL group than the low AL group. Within the high AL group, the fourth and fifth quintiles had significantly elevated odds of elevated blood pressure compared to lowest quintile [OR = 1.92, (95% CI, 1.07, 3.47) and OR =2.28 (95% CI, 1.33, 3.91), respectively]. In the low AL group, none of the quintile effects were significantly different than the referent group although there was evidence of a linear trend (p =0.03). The lead by AL interaction term was not statistically significant for either systolic or diastolic blood pressure models.ConclusionsResults suggest that higher AL may amplify the adverse effects of lead on blood pressure. Future research should assess the implications of cumulative exposures to environmental and social stressors for regulatory decision-making.

Variation in the Calculation of Allostatic Load Score: 21 Examples from NHANES

“…Of these 12 references, three did not use NHANES data and one was included in our original search. Therefore, this review on the calculation of ALS is based on 21 studies which used NHANES data in surveys of various lengths of time between 1988 and 2010[3–23]. …”

The Role of Non-Chemical Stressors in Mediating Socioeconomic Susceptibility to Environmental Chemicals

“…A cross-sectional analysis of NHANES data by Zota et al reported that higher allostatic load (used as a proxy measure of stress, and assessed using a 7-item composite of indicators of cardiometabolic dysregulation) heightened associations between blood Pb and blood pressure [23]. In a longitudinal cohort of older adults in Baltimore, Maryland, Glass et al found heightened effects of bone Pb on cognitive function with greater exposures to self-identified neighborhood psychosocial stressors [43].…”

“…As a result, they may be capturing downstream effects of perceived stress, rather that solely reflecting its occurrence per se. Thus, it remains a topic of some debate as to whether allostatic load, often measured using a composite of cardiometabolic risk factors including CRP, high-density lipoprotein cholesterol, serum triglycerides, and waist-hip circumference [12,23], is indeed an appropriate proxy measure of chronic stress, or rather downstream effects. Given this uncertainty, findings in studies that use allostatic load as a marker of stress per se should be interpreted with some caution.…”

“…The best stress assessments measure all facets of this process; however, this is rarely feasible, and instead most studies measure exposure to a strong chronic stressor, typically one unlikely to be positively appraised (e.g., violence). Some studies have used measures focusing on later stages of the stress process, including negative emotional responses (e.g., anxiety, depression) [20][21][22] or biomarkers of cumulative physiologic wear and tear [12,23].…”

Cumulative Environmental Impacts: Science and Policy to Protect Communities

“…Correlations between race/ethnicity, socioeconomic status, and allostatic load have been established (25,56). Allostatic load may also amplify the adverse effects of environmental chemical exposures, such as lead exposure on risk of hypertension among adults and the effect of housing quality on asthma risk in children (27,49,55,77).…”