Background: Longitudinal data on the normal development of blood lipids and its relationships with body fatness in children and adolescents are limited. Objectives of the current analysis were to estimate trajectories related to age for four blood lipid components and to examine the impact of change in body fatness on blood lipid levels, comparing estimated effects among adiposity indices, in children and adolescents.
Methods: Three cohorts, with a total of 678 children (49.1% female, 79.9% nonblack) initially aged 8, 11, and 14 years, were followed at 4-month intervals (1991-1995). Total cholesterol, low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C), and triglyceride levels were determined in blood samples taken following fasting. Body fatness was measured by five adiposity indices-BMI; percent body fat (PBF); abdominal circumference; and the sums of six and of two skinfold thicknesses. Trajectories of change in blood lipid levels from ages 8 to 18 years were estimated by gender and race. The impact of change in body fatness on lipid levels was evaluated for each index, adjusting for gender, race, and age.
Results: All lipid components varied significantly with age. Total cholesterol decreased by approximately 19 mg/dL from ages 9 to 16 years in girls and more steeply from ages 10 to 17 years in boys. LDL-C decreased monotonically, more steeply in boys than in girls. It was higher among nonblacks than among blacks. HDL-C increased monotonically in girls, mainly from ages 14 to 18 years, but fluctuated sharply among boys. Levels of HDL-C were higher among blacks than among nonblacks. The levels of triglycerides increased from ages 8 to 12 years among girls and, almost linearly, from ages 8 to 18 years among boys. The levels of triglycerides were higher among nonblacks than among blacks. Increase in body fatness was significantly associated with increases in total cholesterol, LDL-C, and triglyceride levels. Significant interactions between the adiposity indices (except for BMI) and gender indicated smaller impacts of change in body fatness on total cholesterol and LDL-C in girls than in boys. The estimated impact on triglycerides was weaker among blacks than among nonblacks, except for PBF. Change in body fatness was negatively associated with HDL-C. The results remained essentially unchanged after adjustments for energy intake, physical activity, and sexual maturation.
Conclusions: Patterns of change with age in blood lipid components vary significantly among gender and racial groups. Increase in body fatness among children is consistently associated with adverse change in blood lipids. Evaluation of blood lipid level should take into account variation by age, gender, and race. Intervention through body-fat control should help prevent adverse lipid levels in children and adolescents.