Relationships of Changes in Height, Weight and Body Mass Index to Changes in Blood Lipids From Age 8 to 18 Years: Project Heartbeat!
Background: To study the relationships of changes in anthropometric variables - height, weight, and body mass index (BMI) - to changes in blood lipids (TC, LDL-C, HDL-C and TG) in children and adolescents aged from 8 to 18 years. Methods and Results: Cohorts of three different age levels 8, 11 and 14 years at baseline were enrolled in the study. Each member of these three cohorts was examined three times per year for up to four years. The composition of the study population and the descriptive statistics for the continuous variables at baseline were summarized. Ethnicity was categorized as Black (21.1%) and non-Black (79.9%). Non-Black includes White (74.6%), Hispanic (3.7%), Asian (1.0%) and American Indian (0.6%). The relationships of changes in anthropometric variables and in blood lipids were evaluated by adding height, weight, or BMI and associated interaction terms separately to the basic age-sex models, derived in previous analyses. A multilevel modeling technique was used. Likelihood ratio tests were conducted by calculating the deviation of -2log(likelihood) within the basic model and alternative models. Height or height gain had significant negative associations with changes in TC, LDL-C and HDL-C with estimated coefficients of -0.763, -0.448 and -0.301, respectively. The estimated coefficients between weight gain and changes in TC, LDL-C and TG were 0.337, 0.370 and 0.1473, respectively, and -0.305 for HDL-C. The estimates of relationships between changes in BMI and in TC, LDL-C, HDL-C and TG were 2.122, 1.884, -0.885 and 4.673, respectively. An interaction between weight (or BMI) and ethnicity was significant in the models for triglycerides only. Sex-Age interactions were significant in most models. Effective effects of race were significant in the models for LDL-C, HDL-C and TG. Conclusions: The results of this longitudinal analysis indicated a very strong association between increasing BMI and changes in blood lipids within the period of childhood and adolescence. These findings have implications for assessing changes in blood lipids, especially among those experiencing the greatest increases in BMI.