Compositional analyses of the associations between sedentary time, different intensities of physical activity, and cardiometabolic biomarkers among children and youth from the United States

Introduction
Compositional data analysis is one appropriate method for co-dependent data, even when
data are collected for a subdivision of the 24-hour period, such as the waking day. Objec-
tives were to use compositional analyses to examine the combined and relative associations
of sedentary time (ST), light-intensity physical activity (LPA), moderate-intensity physical
activity (MPA), and vigorous-intensity physical activity (VPA) with cardiometabolic biomark-
ers in a representative sample of children and youth.
Methods
This cross-sectional study included 2544 participants aged 6–17 years from the 2003–2006
United States National Health and Nutrition Examination Survey. ST (<100 counts per min-
ute), LPA (100 counts per minute to <4 METs; Freedson age-specific equation), MPA (4 to
<7 METs), and VPA (�7 METs) were accelerometer-derived. Cardiometabolic biomarkers
included waist circumference, body mass index (BMI) z-score, HDL-cholesterol, C-reactive
protein, and blood pressure. Triglycerides, glucose, insulin, and LDL-cholesterol were mea-
sured in a fasting sub-sample of adolescents (n = 670). Compositional linear regression
models were conducted.
Results
The composition of ST, LPA, MPA, and VPA was significantly associated with BMI z-score,
log waist circumference, systolic and diastolic blood pressure, HDL-cholesterol, and log
plasma glucose (variance explained: 1–29%). Relative to the other three behaviors, VPA
was negatively associated with BMI z-score (γVPA = -0.206, p = 0.005) and waist circumference (γVPA = -0.03, p = 0.001). Conversely, ST was positively associated with
waist circumference (γST = 0.029, p = 0.013). ST and VPA were also positively associated
with diastolic blood pressure (γST = 2.700, p = 0.018; γVPA = 1.246, p = 0.038), relative to
the other behaviors, whereas negative associations were observed for LPA (γLPA = -2.892,
p = 0.026). Finally, VPA was positively associated with HDL-cholesterol, relative to other
behaviors (γVPA = 0.058, p<0.001).
Conclusions
The ST and physical activity composition appears important for many aspects of cardiome-
tabolic health in children and youth. Compositions with more time in higher-intensity activi-
ties may be better for some aspects of cardiometabolic health