Relationships between skin color, income, and blood pressure among African Americans in the CARDIA Study

OBJECTIVES: We explored how income and skin color interact to influence the blood pressure of African American adults enrolled in the longitudinal Coronary Artery Risk Development in Young Adults (CARDIA) Study. METHODS: Data were derived from 1893 African American CARDIA year-15 participants who had undergone skin reflectance assessments at year 7. We adjusted for age, gender, body mass index, smoking status, and use of antihypertensive medication to examine whether year-15 self-reported family incomes, in interaction with skin reflectance, predicted blood pressure levels. RESULTS: Mean systolic and diastolic blood pressure levels were 117.1 (+/-16.07) and 76.9 (+/-12.5) mm Hg, respectively. After adjustment, the interaction between skin reflectance and income was significantly associated with systolic blood pressure (P\u3c .01). Among lighter-skinned African Americans, systolic pressure decreased as income increased (b= -1.15, P\u3c.001); among those with darker skin, systolic blood pressure increased with increasing income (b=0.10, P=.75). CONCLUSIONS: The protective gradient of income on systolic blood pressure seen among African Americans with lighter skin is not observed to the same degree among those with darker skin. Psychosocial stressors, including racial discrimination, may play a role in this relationship