Muscle mass is the main somatic growth indicator associated with increasing blood pressure with age in children and adolescents.

Studies have shown that lean mass must be an important determinant of blood pressure value in children and adolescents. The absence of adjustment for the collinearity between lean and fat mass (FM), restricted age span, and lack of separate analysis by sex leave a gap in the literature. This study determined direct and indirect effects of the somatic growth indicators linked to the association between age and systolic blood pressure (SBP) in boys and girls. This is a cross-sectional study comprising 1,510 participants (6-18 years). Path analysis was used to test a model in which the association between age and SBP would have a direct and independent component, but also indirect mediating paths through muscle mass (MM), FM, and height. There was no significant association between age and SBP (unstandardized β ± SE) for both girls (0.072 ± 0.236, P = .761) and boys (0.238 ± 0.264, P = .368). Height was not a mediator for the association between age and SBP in both girls (-0.291 ± 0.156, P = .062) and boys (-0.015 ± 0.187, P = .935). Mediating effect of MM was significant for both girls (0.909 ± 0.137, P < .001) and boys (1.341 ± 0.161, P < .001), whereas mediating path through FM was significant only for boys (0.069 ± 0.023, P = .003). In conclusion, muscle mass was the strongest somatic growth indicator associated with the blood pressure value in children and adolescents. Further increase in body fat mass may affect systolic blood pressure more in boys than in girls.