DEVELOPMENT OF CARDIOVASCULAR RISK-FACTORS FROM AGES 8 TO 18 IN PROJECT HEARTBEAT - STUDY DESIGN AND PATTERNS OF CHANGE IN PLASMA TOTAL CHOLESTEROL CONCENTRATION

Background Project HeartBeat! is a longitudinal study of the developme nt of cardiovascular risk factors as growth processes. Patterns of ser ial change, or trajectories, from ages 8 to 18 years for plasma total cholesterol concentration (TC) and percent body fat illustrate the des ign and synthetic cohort approach of the study. Methods and Results Si x hundred seventy-eight children (49.1% female, 20.1% black) entered t he study at ages 8, 11, and 14 years and were followed up with examina tions every 4 months for less than or equal to 4 years. Multilevel ana lysis demonstrated trajectories for population mean values of TC and p ercent body fat in sex-specific synthetic cohorts from ages 8 to 18 ye ars. Polyphasic patterns of change in TC were confirmed, with notable sex differences in age patterns and with minimum mean values of TC of 3.85 mmol/L for females and 3.59 for males. As illustrated by data for males, the approximate 75th percentile values of mean TC ranged from 4.78 mmol/L at its early peak to 4.06 at its late-teen nadir. Percent body fat exhibited a trajectory closely parallel with that for TC only for males and appeared to be unrelated for females. Conclusions The p olyphasic trajectory for TC from ages 8 to 18 years differs between fe males and males, indicates marked age variation in 75th percentile val ues and, in males only, closely parallels the trajectory for percent b ody fat. These and other results indicate the value of both follow-up every 4 months across age intervals to detect rapid risk factor change and the synthetic cohort approach for gaining new insights into the d ynamics and possible determinants of this change from ages 8 to 18 yea rs.