OBESITY INDEXES AND CVD RISK FACTORS

The study is designed to use existing data from the Bogalusa Heart Study,
a community based study of the early natural history of CVD in an entire
free-living population of white and black children, adolescents and young
adults, to examine the relationships between obesity and other risk factors
for cardiovascular disease (CVD). The design of the Bogalusa Study is
mixed; cross-sectional and longitudinal data have been collected. Using
data from surveys conducted during 1978-79 (n=3,590 children and
adolescents, aged 15-17 yrs) and 1984-86 (n=3,175 children, adolescent and
young adults, aged 8-27 yrs), in cross-sectional analyses, we aim to
determine critical levels of total body fat and fat pattern that are
associated with elevated CVD risk factors in young adults. Also, in
longitudinal analyses, we aim to determine whether childhood and adolescent
obesity is predictive of subsequent elevated levels of CVD risk factors and
to determine the extent to which change in body composition is related to
change in risk factors. The CVD risk factors to be examined in relation
to obesity include systolic and diastolic blood pressure, total
cholesterol, triglycerides, lipoproteins (HDL, LDL, VLDL), lipoprotein
ratios and serum insulin. Several indices of body composition (obesity)
will be examined including total body percent fat, skinfold and body mass
index percentile rankings, and fat pattern (logN (subskf/triskf) and we
intend to compare their tracking, sensitivity and specificity, and positive
and negative predictive values. The complete data sets from each survey
will be used to calculate age-, race- and sex-specific percentiles for
skinfolds, BMI and CVD risk factors in children and adolescents. In a
recent investigation in children and adolescents we have shown males with
>_25% fat and females with >_30% fat have a significantly greater risk of
elevated CVD risk factors than their leaner peers. In the proposed study
we intend to use the cross-sectional data from males and females collected
during 1984-1986 to test the hypothesis that similar levels of body fat
will be associated with greater risk of elevated CVD risk factors in young
adults. For this analysis, elevated levels of CVD risk factors will be
defined according to nationally recommended criteria for adults. The
longitudinal analyses will be conducted using data from 1900 males and
females who were first examined in 1978-1979 as children and adolescents
and who were retested 5-8 years later in 1984-1986 as adolescents and young
adults. Although we have previously established critical levels of body
fat associated with elevated risk factors in children and youth, the degree
to which these levels of body fat track and are predictive of future levels
of risk factors is not known. The direct comparisons of tracking,
sensitivity, specificity, and positive and negative predictive value among
the different indices of obesity will allow us to assess whether childhood
and adolescent obesity is predictive of future risk and which index of
obesity is most useful. The information to be gained from the proposed
analyses is unique and essential for the design of screening programs for
early intervention and prevention of CVD.