Interaction of Social Factors and Environmental Pollutants in Black-White Health Disparities: The Case of Lead and Hypertension.

Abstract

The black-white disparities in hypertension have been well-documented for decades. Disparities in the social and physical environments are thought to be fundamental determinants of the disparities in hypertension. In addition to their independent effects, the social and physical environments may interact to result in hypertension. Social stress, in particular, has been shown to amplify the harmful effects of environmental pollutants. To date, no one has examined the notion that social stress and environmental pollutants interact to produce and maintain black-white hypertension disparities. To test this interaction, I focus on the documented finding from previous studies that there is a positive association between blood lead and blood pressure in black but not white adults. In this dissertation, I hypothesize that black-white disparities in social stress amplify the harmful effects of lead to result in an effect of blood lead on blood pressure for black but not white adults.

Using data from the National Health and Nutrition Examination Survey (NHANES) 2001-2006, I examine the role of depressive symptoms, as a proxy of psychosocial stress, and educational attainment and poverty status, as proxies of socioeconomic constraints and resources, in the lead-blood pressure association.

Black women who report high levels of depressive symptoms show a 7.2mmHg increase in systolic blood pressure for each doubling of blood lead (p<0.05) while black women who report low levels of depressive symptoms show a 1.2mmHg increase (p=NS). Black men show a similar pattern. Black men without a high school education experience a 4.9mmHg increase (p<0.001) in systolic blood pressure for each doubling of blood lead, while black men with at least a high school education experience a 2.0mmHg increase (p<0.05). Black women do not show this pattern. Both poor and nonpoor black men and women show similar increases in systolic blood pressure due to lead. Overall, these results suggest that social factors can amplify the harmful effects of lead.