Reproducibility of ambulatory blood pressure measures in African-American adolescents

Objective: The primary purpose of this study was to evaluate the reproducibility of ambulatory blood pressure (BP) measures in African-American (AA) adolescents. Methods: Forty-one AA adolescents (age 16.6 ± 1.3 yrs, 16F) with high-normal BP were measured on 3 occasions at 2-month intervals. Systolic BP (SBP), diastolic BP (DBP), and heart rate (HR) measures were recorded using the Spacelabs ambulatory BP monitor 90207 (Redmond, Wash) in the natural environment over 24-hour periods. Mixed model repeated measures ANOVAs were used to analyze the underlying error variance-covariance (V-C) structures as well as mean differences for the 3 visits. Results: Daytime measures: there were no significant mean differences across visits for daytime SBP, DBP, and HR (all Ps>.57). The error V-C matrix was heterogeneous Toeplitz for daytime SBP. Correlations between visits 1 and 2, 1 and 3, and 2 and 3 for daytime SBP were rs=0.71, 0.47, and 0.71, respectively. Compound symmetry (CS) was the preferred model for daytime DBP (r=0.68) and HR (r=0.75). Nighttime measures: there were no significant mean differences across visits for nighttime SBP, DBP, and HR (all Ps>.29). The error V-C matrix was unstructured for nighttime SBP. Correlations between visits 1 and 2, 1 and 3, and 2 and 3 for SBP were rs=0.74, 0.33, and 0.33, respectively. CS was preferred for night-time DBP (r=0.58) and HR (r=0.74). Conclusion: Collectively, these findings demonstrate that 3 measurements of ambulatory-derived DBP and HR measures are stable across 4 months, but SBP was only stable across 2 months in African-American adolescents.