A novel look at racial health disparities: the interaction between social disadvantage and environmental health

Abstract

Objectives: We explored the notion that social disadvantage increases vulnerability to the health effects of environmental hazards. Specifically, we examined (1) whether race modifies the association between blood lead and blood pressure and (2) whether socioeconomic status (SES) plays a role in this modifying effect.

Methods: Using the National Health and Nutrition Examination Survey (2001-2008) and linear regression, we estimated the association between blood lead and blood pressure. Using interactions among race, SES, and lead, we estimated this association by levels of social disadvantage.

Results: Black men and women showed a 2.8 (P < .001) and 4.0 (P < .001) millimeters mercury increase in SBP, respectively, for each doubling of blood lead. White adults showed no association. This lead-SBP association exhibited by Blacks was primarily isolated to Blacks of low SES. For example, poor but not nonpoor Black men showed a 4.8 millimeters mercury (P < .001) increase in SBP for each doubling of blood lead.

Conclusions: Our results suggest that social disadvantage exacerbates the deleterious health effects of lead. Our work provides evidence that social and environmental factors must be addressed together to eliminate health disparities.

FIGURE 1—

Association between blood lead and systolic blood pressure by race–education group, for (a) men and (b) women: National Health and Nutrition Examination Survey, United States, 2001–2008. Note. SBP = systolic blood pressure. All results were weighted to account for complex survey design. Regression models controlled for age, age, hematocrit, body mass index, heavy alcohol use, smoking status (never, former, current),diabetes diagnosis, family poverty income ratio, antihypertensive medication use, and dietary intake of sodium, calcium, and potassium. Log-transformed blood lead level, on the x-axis, is that for each decile of the gender-specific distribution.

FIGURE 2—

Association between blood lead and systolic blood pressure by race-poverty group, stratified by gender: National Health and Nutrition Examination Survey, United States, 2001–2008. Note. PIR = poverty income ratio; SBP = systolic blood pressure. All results were weighted to account for complex survey design. Regression models controlled for age, age, hematocrit, body mass index, heavy alcohol use, smoking status (never, former, current), diabetes diagnosis, education (< high school, high school, > high school), and antihypertensive medication use, and dietary intake of sodium, calcium, and potassium. Log-transformed blood lead level, on the x-axis, is that for each decile of the gender-specific distribution. The PIR is the ratio of the family’s gross income to the family’s poverty threshold as determined annually by the US Census Bureau.