DETERMINANTS OF OFFICE BLOOD PRESSURE VARIABILITY AND INSTABILITY IN CHILDREN, ADOLESCENTS AND YOUNG ADULTS

Abstract

Objective: To evaluate the determinants of office blood pressure (BP) variability and instability within a single visit in young individuals. Design and method: Apparently healthy individuals aged 6-25 years referred for elevated blood pressure (BP) were subjected to triplicate office BP measurements in a single visit and 24h ambulatory BP monitoring. BP variability and instability were assessed separately for systolic and diastolic BP using: (i) standard deviation (SD) (ii) coefficient of variation (CV) (iii) average real variability (ARV) (iv) maximum office BP (Max) (v) maximum-minimum office BP difference (MMD) (vi) ratio of difference between 1st-3rd measurement to the average office BP (Relative change). White-coat effect was defined as the difference between office and daytime ambulatory BP. Results: 320 individuals were analyzed (mean age 13.6±3.6 years, 66.8% males, BMI z-score 1.12±0.96, average office BP 122.6±16.6/72.6±10.7 mmHg, 24h ambulatory BP 119.3±11.5/67.8±6.8). Based on office and 24h ambulatory BP, 21.3% of the participants had white-coat hypertension, 8.1% masked and 16.6% sustained hypertension. Age was associated with SD (r = 0.23, p<0.001), CV (r = 0.11, p<0.05), Max (r = 0.54, p<0.001) and MMD (r = 0.23, p<0.001) of office systolic BP, and Max (r = 0.29, p<0.001) and ARV (r = 0.12, p<0.05) of diastolic. In multivariable log-linear regression models [(independent variables: age, sex, BMI z-score, heart rate, office BP, white-coat effect (> = 5/6 mmHg systolic/diastolic, 75th centile)], office BP was an independent determinant for indices of systolic BP variability and instability [SD (↓ = 0.01, p<0.001), ARV (↓ = 0.01, p<0.001), Max (↓ = 0.01, p<0.001), MMD (↓ = 0.01, p<0.001) and Relative change (↓ = 0.001, p<0.05)], and for CV (↓ = -0.06, p<0.001) and Max (↓ = 0.01, p<0.001) of diastolic. White-coat effect was a significant determinant for CV of office systolic BP (↓ = 0.15, p<0.05) and Relative change of office diastolic BP (↓ = 0.03, p<0.05). Conclusions: These results suggest that in healthy children, adolescents, and young adults the indices of office BP variability and instability within the first visit seem to be determined by the level of office BP and the magnitude of the white-coat effect.