High Systolic Blood Pressure of High-Income African American Children

According to the Minorities' Diminished Returns (MDRs) theory, racism may reduce the health returns of family socioeconomic status (SEP) resources such as family income for racial minorities, particularly African Americans, compared to Whites. However, we are unaware of any previous studies on racial variation in the protective effects of family income on children's blood pressure.

We conducted this study to compare the overall effects of family income on pre-adolescents' systolic and diastolic blood pressure, test racial variation in this effect, and investigate whether racial variation in this regard is due to racial differences in body mass index.

In this cross-sectional study, we analyzed data from 4007 racially diverse US children 9-10 years old. The independent variable was family income measured as a three-level categorical variable: less than $50 K USD, 50-100 K USD, and 100 + K USD. The primary outcomes were systolic and diastolic blood pressure measured up to three times at 1-min time intervals. Body mass index was the mediator. Mixed-effects regression models were used for data analysis to adjust for data nested to the centers, families, and individuals. Age, gender, parental education, family structure, and Latino ethnicity were covariates.

In the pooled sample and in the absence of interaction terms in the model, family income did not show an inverse association with children's systolic (for 100 + K USD family income: β =  - 0.71, p = 0.233 and for 50-100 K USD family income: β = 0.01, p = 0.989) or diastolic blood pressure (for 100 + K USD family income: β =  - 0.66, p = 0.172 and for 50-100 K USD family income: β = 0.23, p = 0.600). However, race showed a significant interaction with family income on systolic blood pressure (for 50-100 K USD × African American: β = 2.75, p = 0.034), suggesting higher systolic blood pressure of African American adolescents from high-income backgrounds. Racial variation in the protective effect of family income on systolic BP was no more significant (for 50-100 K USD × African American: β = 2.14, p = 0.149) after we controlled for body mass index (BMI), which was higher for African American than White adolescents.

The association between high family income and reduced systolic blood pressure in pre-adolescence might be weaker for African Americans compared to Whites, a difference that African American adolescents' higher body mass index can explain.