The mediating role of adiposity in the longitudinal association between cardiorespiratory fitness and blood pressure in adolescents: LabMed cohort study.

BACKGROUND The aim of this prospective cohort study was to examine if the association between the cardiorespiratory fitness (CRF) at baseline and blood pressure (BP) at follow-up is mediated by adiposity in adolescents. MATERIALS AND METHODS The sample comprised 734 adolescents (349 girls) aged 12-18 years from the LabMed Physical Activity Cohort Study. The variables of interest were measured in 2011 (baseline) and in 2013 (2-year follow-up). CRF was assessed by the 20-meter shuttle run test. Body mass index, waist circumference, body fat percentage, pubertal status and resting BP were assessed according to standard procedures. Boot-strapped mediation procedures were performed and indirect effects (IE) with confidence intervals (CI) not including zero were considered statistically significant. RESULTS After adjusting for potential confounders, body mass index acted as a mediator of the relationship between CRF and systolic BP (IE= -0. 023; CI= -0.039; -0.009), pulse pressure (IE= -0.023; CI= -0.034; -0.012) and rate product pressure (IE= -2.839; CI= -5.329; -0.340). Similar results were obtained for waist circumference as mediator for systolic BP (IE= -0.019; CI= -0.033; -0.005), pulse pressure (IE= -0.017; CI= -0.028; -0.007) and rate product pressure (IE= -3.793; CI= -6.097; -1.689). Likewise, body fat percentage mediated the association for: systolic BP (IE= -0.029; CI= -0.048; -0.010), pulse pressure (IE= -0.027; CI= -0.041; -0.013) and rate product pressure (IE= -4.280; CI= -7.488; -1.264). CONCLUSIONS Adiposity mediated the association between CRF and BP in adolescents. Therefore, both optimal CRF and adiposity levels are important to maintain normal BP ranges throughout adolescence.