Cardiovascular reactivity in Black and White siblings versus matched controls.

Elevated cardiovascular (CV) reactivity may be a marker or mechanism for the early development of essential hypertension (EH) and may contribute to the greater prevalence of EH observed in Black adults. Previous research has demonstrated that Black children show greater CV reactivity than White children to psychological stressors, however, the role of heritability in understanding these racial differences is still unknown. Evidence which supports a genetic influence on CV reactivity comes from animal studies, research on family history of EH, and from twin and sibling studies. The present study expands on previous findings by examining racial differences in CV reactivity in 15 pairs of Black siblings, 15 pairs of age-and sex-matched unrelated Black control subjects, 17 pairs of White siblings, and 17 pairs of age-and sex-matched unrelated White control subjects. Systolic blood pressure (SBP), diastolic blood pressure (DBP), and heart rate (HR) measurements were obtained at rest and during a stress task (competitive video game). Black siblings demonstrated a significantly higher intraclass correlation for DBP reactivity than Black controls or White siblings (r=0.73, versus 0.16, 0.14, respectively). Additionally, Black siblings demonstrated a steeper rise and then a plateau in DBP and HR reactivity to the video game task, while White siblings showed a more gradual increase in these measures over the course of playing three video games. The results for DBP and HR reactivity, however, were not consistent among either of the matched control groups. These results expand on previous research by suggesting a stronger genetic influence of CV reactivity in Black than in White children.