Blood Pressure Variability and Classification of Prehypertension and Hypertension in Adolescence
Falkner B, Gidding SS, Portman R, Rosner B
Pediatrics. 2008;122:238-242
Summary
Since 2004, the concept of "prehypertension" has been used to label children and adolescents with blood pressures above expected ranges but not yet high enough to be considered hypertensive. The idea was that prehypertensive children were at higher risk for later cardiovascular disease than normal blood pressure peers. For adolescents, the cutoff for diagnosing prehypertension is a blood pressure higher than 120 systolic or 80 diastolic, but the levels are lower for younger children based on their height percentile, gender, and age.
The authors examined follow-up blood pressure results from the children enrolled in the 2004 study that produced the guidelines in order to evaluate the variability of blood pressure in teens and to determine the rate of progression from prehypertension to hypertension. The repeat blood pressures were collected at approximately 2 and 4 years after the original ones. The authors evaluated the participants in the original study who were 13-15 years old at initial enrollment and measurement. They were therefore 15-17 and 17 years old at the 2- and 4-year follow-up points (17 was the last age measured at any point).
The authors defined prehypertension as 120/80 or higher or at or above the 90th percentile for systolic or diastolic blood pressure (adjusted for age, gender, and height), choosing the lower value when they were different. Children with systolic or diastolic blood pressures at or above the 95th percentile were considered hypertensive. There were over 4000 males and over 4000 females in the current study. At baseline, 21% of males and 13% of females had prehypertension.
For males, 14% of those who were prehypertensive were hypertensive at the 2-year point, and the rate was 12% for prehypertensive females becoming hypertensive. The changes were notable among the prehypertensive groups, however, with 37% of male prehypertensives and 63% of female prehypertensives measuring in the normal blood pressure range at the 2-year point. Even large percentages of the hypertensive males (23%) and females (47%) had normal blood pressures at 2 years. The rates were very similar when comparing baseline blood pressures to 4-year blood pressures.
Taking the progression from baseline to 2 years, the authors concluded that the rate of progression from prehypertension to hypertension was around 7% per year.
Viewpoint
The authors noted that the variability in these blood pressures reinforces the recommendation to measure blood pressure twice at each visit and to document elevated blood pressure at more than one visit in order to confirm diagnoses of prehypertension or hypertension. This study does document that some progression happens in adolescents and confirms the need for monitoring blood pressure over time as part of routine health maintenance visits.
Abstract