Background and objectives: Information on ambulatory blood pressure monitoring (ABPM) in children is scarce. While in adults office BP (OBP) is higher than ABP and the difference increases as OBP increases, information in children suggests that at this young age ABP is no lower and often higher than OBP. This study was aimed at describing OBP-ABP differences in a cohort of children of different ages and BPs, and investigating whether OBP-ABP differences are dependent on age or OBP level.
Methods: We retrospectively compared OBP and 24-h, daytime and night-time ABP in 433 children and adolescents aged 4-18 years, referred to our hospital clinic.
Results: OBP was found to be significantly lower than 24-h and daytime ABP in the low age tertile (4-10 years) but not in the medium and high tertiles. OBP was also lower than ABP in normotensive patients (n = 182), but higher than ABP in untreated hypertensive patients (n = 92) despite similar ages. Continuous analyses showed a weak correlation of OBP-ABP differences with age, and a much stronger correlation with OBP so that 24-h ABP was higher than OBP at OBP values less than 117/73 mmHg and lower than OBP at higher OBP values. Logistic regression analysis indicates that also in children OBP accounts for most of the OBP-ABP difference.
Conclusion: There is a common relation both in children and adults between OBP and ABP. It is only because high OBP is common in the elderly, and the lowest OBP is usually found in young children that large positive OBP-ABP differences have been associated with old age, and negative differences with childhood. OBP-ABP differences, often defined as white-coat effect, can have different directions and are likely to be largely due to regression to the mean.