Intensified effect of adiposity on blood pressure in overweight and obese children

Abstract

In children, blood pressure (BP) and risk for hypertension are proportional to degree of adiposity. Whether the relationship to BP is similar over the full range of adiposity is less clear. Subjects from a cohort study (n=1111; 50% male and 42% black) contributed 9102 semiannual BP and height/weight assessments. The mean enrollment age was 10.2 years, and mean follow-up was 4.5 years. Adiposity was expressed as body mass index percentile, which accounted for effects of age and sex. The following observations were made. The effect of relative adiposity on BP was minimal until the body mass index percentile reached 85, beginning of the overweight category, at which point the effect of adiposity on BP increased by 4-fold. Similarly intensified adiposity effects on BP were observed in children aged ≤10, 11 to 14 years, and ≥15 years. Serum levels of the adipose tissue-derived hormone, leptin, together with heart rate, showed an almost identically patterned relation to BP to that of body mass index percentile and BP, thus implicating a possible mediating role for leptin. In conclusion, there is a marked intensification of the influence of adiposity on BP when children reach the categories of overweight and obese. Among the possible pathways, leptin may be a potentially important mediator acting through the sympathetic nervous system (reflected in heart rate). The findings have relevance to interventions designed to prevent or treat adiposity-related increases in BP and to the analytic approaches used in epidemiological studies.

Figure 1

Comparisons of the BMI percentile effects on systolic BP percentile for normal weight and overweight children of different age groups. Purple bars represented the estimated adiposity effects on BP in overweight and obese children; yellow bars represented the estimated adiposity effects on BP in normal weight children. Green bars represented the adiposity effect estimates when no BMI percentile cutoff point was used. The figure showed that without weight status stratification, one could severly underestimate the adiposity effects on BP in overweight and obese children, and overestimates the effect in normal weight children. Top panel: Estimates for children 10 years of age or younger. Middle panel: Estimates for children 11 to 14 years of age. Bottom panel: Estimates for children 15 years of age or older. The figure showed that adiposity effects on BP were similarly intensified in overweight and obese children of all age groups.

Figure 2

Estimated probability of BP reaching prehypertension (pre-HTN) and hypertension (HTN) levels. The black lines are smooth functions of the BMI percentile from semiparametric logistic regression analysis, and the purple lines are from the piece-wise linear logistic regression analysis with an inflection point at the 85^th percentile of BMI. The green bands represent the 95% confidence intervals for the mean proportion of BP measurements in the pre-HTN/ HTN levels estimated from the piece-wise logistic regression analysis.

Figure 3

Estimated levels of serum leptin concentration (a) and heart rate (b) at different BMI percentiles. Estimated levels of systolic blood pressure percentile (c) and heart rate (d) at different levels of serum leptin concentration.