Influence of blood pressure level and age on within-visit blood pressure variability in children and adolescents

Blood pressure (BP) is variable in children and this could affect BP assessment, but the magnitude of within-visit BP variability (BPV) over consecutive measurements has never been investigated. This study aimed to determine the direction and magnitude of, and factors affecting, within-visit BPV in children and adolescents. BP was recorded among 3047 children (aged 12 years [95%CI 12, 13], males 52%) from the 2011-2013 Australian Health Survey. BPV was defined as the absolute difference (a dagger SBPABS) between the first (SBP1) and second systolic BP (SBP2) and the overall variability in three measures when available (SBPV). On average, a dagger SBPABS was 6.7 mmHg (95%CI 6.3, 7.0) and SBPV was 8.2% (95%CI 7.8, 8.6). a dagger SBPABS was greater with higher BP levels but lower with older age. From first to second measurements, SBP decreased in 58% (95%CI 56, 60), did not change in 10% (95%CI 9, 12), and increased in 32% (95%CI 29, 34) of the population. Conclusions: BP is highly variable in children and adolescents, with the magnitude of variability being associated with both age and BP level. SBP increases on repeat measurement in a substantial proportion of the population. The optimal protocol of BP assessment to address this increased BPV needs to be determined. What is Known: Diagnosis of elevated blood pressure (BP) is based on strict probabilistic criteria, the difference between the 90th (pre-hypertension) and 95th (hypertension) percentiles only being 3-4 mmHg. BP variability could affect BP classification among children and adolescents. What is New: The magnitude of BP change among children and adolescents is highly affected by BP level and age. BP does not always drop on consecutive measurements, and evidence-based BP assessment protocols should be established to avoid misdiagnosis of hypertension.