Persistence of elevated blood pressure during childhood and adolescence: a school-based multiple cohorts study.

Objective: Blood pressure (BP) screening is advocated in children. However, identification of children with sustained elevated BP is difficult because of high BP variability. We assessed the tracking of BP and the persistence of elevated BP across childhood and adolescence.
Methods: Three cohorts of children from schools in the Seychelles were examined on two occasions at 3-4-year intervals. Obesity was defined as BMI at least 95th sex-specific, and age-specific percentile. On each visit, BP was based on the average of two readings and elevated BP was defined as BP at least 95th sex-specific, age-specific, and height-specific percentile.
Results: Data was collected in 4519 children of mean ages of 5.5 and 9.2 years, 6065 of ages of 9.2 and 12.5 years, and 5967 of ages of 12.5 and 15.6 years, respectively. Prevalence of elevated BP was 10% at age 5.5 years, 10% at 9.2 years, 7% at 12.5 years, and 9% at 15.6 years, respectively. Among children with elevated BP at the initial visit, the proportions who had elevated BP at the subsequent visit 3-4 years later was 13% between ages of 5.5 and 9.2 years, 19% between 9.2 and 12.5 years, and 27% between 12.5 and 15.6 years. These proportions were higher among obese children with elevated BP, that is, 33, 35, and 39%, in each cohort, respectively. Tracking coefficients were slightly larger for SBP (range of tracking coefficients: 0.23-0.40) than for DBP (range: 0.19-0.35), and increased with age. By comparisons, tracking coefficients for BMI were much higher (range: 0.74-0.84).
Conclusion: During childhood and adolescence, having an elevated BP on one occasion is a weak predictor of elevated BP 3-4 years later. Tracking is, however, larger in older and obese children than in younger and nonobese children.