A longitudinal study of ethnic differences in ambulatory blood pressure patterns in youth

Background: Many studies demonstrated an ethnic difference in ambulatory blood pressure (BP) patterns. We examined: 1) the stability of this difference; 2) demographic and anthropometric characteristics that predict the difference over 2 years; and 3) the clinical significance of the difference. Methods: Recordings were performed 2 years apart on 94 African American and 92 European American youths with a positive family history of hypertension, aged 14 ± 2 years at initial testing. Results: African Americans had higher nighttime systolic BP (SBP) on the initial (109 ± 9 ν 105 ± 8 mm Hg; P < .001) and follow-up (110 ± 10 ν 105 ± 8 mm Hg; P < .0001) visits despite similar daytime SBP. This was associated with greater left ventricular mass/height^2.7 (LVM/height^2.7) during the initial (31 ± 8 ν 28 ± 6 g/height^2.7; P < .01) and follow-up (32 ± 8 ν 28 ± 8 g/height^2.7; P < .02) visits. Sex accounted for 17% (P < .0001) of the variance of follow-up daytime SBP in African Americans, and age for an additional 10% (P < .001). In comparison, initial height accounted for 11% (P < .001) of the variance in European Americans. Sex accounted for 18% (P < .0001) of the variance of follow-up nighttime SBP in African Americans, age for an additional 12% (P < .0001), and initial LVM/height^2.7 an additional 6% (P < .02). In contrast, sex accounted for 13% of the variance of follow-up nighttime SBP in European Americans, and initial height accounted for an additional 8% (P < .004). Conclusions: The pattern of higher nighttime BP despite similar daytime BP in African Americans is stable over time, with sex as the most important predictor of nighttime BP in both groups. This study provides confirmatory data on the clinical significance of the differences.