Tracking of blood pressure in children and adolescents in Germany in the context of risk factors for hypertension

Background:

Blood pressure (BP) tracks from childhood to adulthood. Tracking has two aspects: the stability of the ranking relative to others over time and prediction of future values from baseline values. This study investigates BP tracking in children and adolescents in Germany in the context of hypertension risk factors.

Methods:

BP was measured in 2686 participants of the German Health Examination Survey for Children and Adolescents (KiGGS) (t0 2003 – 2006; age 3 – 17 years) and of its six-year follow-up „Motorik Modul“ (MoMo) (t1 2009 – 2012; age 9 – 24 years). BP tracking coefficients were calculated from Spearman“s rank-order correlations. Logistic regression models were used to predict t1-BP above the hypertension threshold (>= P95 KiGGS-references for age < 18; >= 140/90 mmHg for age >= 18) from t0-BP and from baseline and follow-up hypertension risk factors.

Results:

BP tracking in the sense of BP ranking relative to others was moderate (Spearman rank correlation coefficients in age- and sex subgroups 0.33 – 0.50 for SBP and 0.19 – 0.39 for DBP). There were no statistically significant differences between sex and age groups. Baseline hypertensive BP was the strongest independent predictor of hypertensive BP after 6 years (OR 4.3 and 4.1 for age groups 3 – 10 and 11 – 17y) after adjusting for sex, BMI trajectories, birthweight, parental hypertension, and – age-group dependent – sports/physical activity/aerobic fitness. However, the corresponding positive predictive value of baseline hypertensive BP for hypertensive BP six years later was only 39% (95% CI 31 – 47) (3 – 10y) and 34% (95% CI 22 – 48) (11 – 17y), the negative predictive value of non-hypertensive baseline BP was 88% (95% CI 86 – 89) and 87% (95% CI 83 – 90) respectively.

Discussion:

Our analysis shows with recent population-based data from Germany that BP in children and adolescents tracks only moderately over six years. BP in childhood is the strongest independent predictor of future BP but its predictive value is limited.