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Excerpt
All that is known about the levels and distribution of casual blood pressure in childhood and adolescents is that blood pressure increases during growth and maturation, and adolescence is a fast growth period during which body mass and blood pressure change rapidly. These are the main reasons why reference blood pressure values over the last few decades have been referred to as specific for sex, age, and/or height in children and adolescents up to 18 years of age.
Based on the above, normal blood pressure is defined by the Task Force as systolic and diastolic blood pressure less than the 90th percentile for age, sex and height. Borderline, or high-normal blood pressure, is defined as an average systolic and/or average diastolic blood pressure between the 90th and 95th percentiles for age, sex and height. Hypertension is defined as an average systolic and/or average diastolic blood pressure greater than the 95th percentile for age, sex and height, measured on at least three separate occasions [3].
Statistically, 5% of children have a blood pressure measurement higher than the 95th percentile during a single office visit. However, blood pressure tends to normalize on subsequent measurements due to the accommodation of the child to the measurement procedure and to the statistical phenomenon of regression towards the mean. Consequently, the prevalence of hypertension decreases to 1% after the second examination [4].
Considering that the prevalence of essential hypertension is low and that there is little immediate risk to most children, can routine blood pressure measurements as part of pediatric care be justified? Blood pressure tracks from childhood to adulthood; therefore, some have recommended screening to identify those children at risk for the development of essential hypertension as adults. Others have argued against this strategy because they believe that correlations between childhood and adult blood pressure levels are too weak. These viewpoints call into question the usefulness of routine blood pressure measurements to identify children at high risk for the development of essential hypertension.
Few large-scale epidemiologic studies have revealed long-term persistent elevated blood pressure from childhood into adulthood and, more importantly, how the persistent elevation in blood pressure ultimately has developed into adult hypertension [5,6]. Unfortunately, some aspects of design and methodology differ among the studies, making it difficult to pool data.
The degree of blood pressure tracking has been shown to vary among studies demonstrating positive correlations, from low to high magnitude [5–9]. In general, a lower correlation was found for diastolic blood pressure compared to systolic blood pressure [9]. The differences among the studies with respect to the strength of the juvenile–adult blood pressure correlations may be due to the differences in ages of children at entry, in adult outcome ages, in blood pressure recording and in the time of follow-up. The same happens with studies which analyse the risk to develop hypertension.
