Fat-Free Mass May Play a Dominant Role on the Association Between Systolic Blood Pressure and Body Composition in Children and Adolescents.

Systolic blood pressure (SBP) significantly associates with body composition in children and adolescents. However, which components of body composition is the dominant contributor to SBP in children and adolescents remains unclear. We therefore aimed to determine the dominant contributor to SBP among components of body composition in a large cohort of American children and adolescents derived from the National Health and Nutrition Examination Survey with cross-sectional analysis. 13618 children and adolescents (median age 13 years; 6107 girls) with available data on whole-body dual-emission X-ray absorptiometry measurements were included. Multiple linear regression showed that SBP associated with higher total fat-free mass in boys (β=0.49, P<0.001) and girls (β=0.47, P<0.001) and with higher total fat mass only in boys (β=0.12, P<0.001), after adjustment for covariates. When taking fat distribution into consideration, SBP associated with higher trunk fat mass (Boys: β=0.28, P<0.001; Girls: β=0.15, P<0.001), but negatively associated with leg fat mass (Boys: β=-0.14, P<0.001; Girls: β=-0.11, P<0.001), in both boys and girls. Dominance analysis showed that total fat-free mass was the dominant contributor to SBP (boys: 49%; girls: 55.3%), followed by trunk fat mass (boys: 32.1%; girls: 26.9%); leg fat mass contributed the least to SBP in boys (18.9%) and girls (17.8%). Our findings indicated that total fat-free mass was not only associated with SBP, but also the most dominant contributor to SBP variation in American children and adolescents.