Abstract P057: Heterogeneity in Blood Pressure and Lipid Trajectories throughout Childhood: Project HeartBeat!

Background: Previous studies have examined blood pressure (BP) and lipid changes through childhood and adolescence using population averages. We hypothesized that trajectories for these are heterogeneous, with sub-groups of the population showing different patterns in BP and lipid changes through childhood and adolescence. Methods: This study includes 678 children in Project HeartBeat!. Children were ages 8, 11, or 14 at baseline in 1991 and were examined every 4 mos for up to 4 yrs (mean number of exams, 8). At each exam, lifestyle, anthropometric and laboratory data was collected. Group-based modeling (PROC TRAJ) was used to identify trajectories in systolic BP (SBP), fifth phase diastolic BP (DBP5), total cholesterol (Chol), HDL Chol, LDL Chol and triglycerides as a function of age. The optimal number of race- and sex-adjusted trajectories was determined using the Bayesian Information Criterion and clinical expertise. Results: Among 678 children (49% female; 75% nonblack), 314 were enrolled at age 8, 197 at age 11, and 167 at age 14. Four distinct BP trajectories were identified (figure panels A-B). For SBP the low, low-intermediate, high-intermediate and high groups contained 16.4%, 36.3%, 34.5% and 12.7% of the sample, respectively; for DBP5, they contained 9.5%, 34.2%, 41.0%, and 15.3%. Three trajectories were identified for lipids (panels C-F). The low, intermediate, and high groups included 43.9%, 49.0% and 7.0% of the sample for total Chol, respectively. Corresponding figures were 33.4%, 49.3%, and 17.2% for HDL; 33.5%, 53.9%, and 12.7% for LDL; and 75.3%, 20.3%, and 4.5% for triglycerides, respectively. Girls were less likely (39% vs 61%) to be in the highest SBP groups as compared to the lowest. Blacks were more likely to be in the higher risk trajectories for DBP5 and HDL (p<0.01). Conclusion: Significant heterogeneity exists in BP and lipid trajectories throughout childhood. Finding predictors of the low and high trajectory classes may help target interventions to preserve low risk and manage high risk for future CVD.

Abstract P267: Cardiorespiratory Fitness Does not Attenuate the Association Between Adiposity and Blood Lipids in Children and Adolescents: Project HeartBeat! (1991-1995)

Background: Higher levels of adiposity are associated with unfavorable blood lipid levels in pediatric populations. However, little is known about the extent to which cardiorespiratory fitness attenuates this association. Methods: Participants ages 8-16 years (n=256) with valid measures of blood lipids, cardiorespiratory fitness (CRF) and adiposity were examined from Project Heartbeat!, a longitudinal study of cardiovascular risk factors among children and adolescents. CRF was assessed by maximum oxygen uptake: VO 2max (mL/kg/min) measured during treadmill testing and adiposity was assessed by percent body fat (PBF) estimated using sex-specific formulas incorporating bioelectric impedance and six-site skinfold measures. Fasting blood lipids included total cholesterol (TC), triglycerides (TG), low density lipoprotein cholesterol (LDL-C) and high density lipoprotein cholesterol (HDL-C). Linear regression was used to quantify cross-sectional associations between CRF and adiposity with blood lipids by sex and pubertal status (Tanner stage 1 vs. 2-5). Results: When examined individually, higher PBF and lower VO 2max were associated with more favorable levels of blood lipids in pre-pubertal boys, however, the associations were not consistent across all sex/puberty groups (Table 1). In multivariate models where both VO 2max and PBF were included, PBF remained significant for all blood lipids in pre-pubertal boys but only with TC and LDL-C in pre-pubertal girls. Among pubertal participants, only TG remained significantly associated with PBF when similarly accounting for VO 2max . Conclusions: Prior to the onset of puberty, higher adiposity is independently associated with more favorable levels of TG and HDL-C in boys and TC and LDL-C in girls even after accounting for CRF. During puberty, the majority of these associations are greatly attenuated, which further highlights the complexities associated with examining correlates of blood lipids in developing children.