Fitness, waist circumference and their association with future blood pressure in youth: The UP&DOWN Longitudinal Study

Objectives: The aim was to determine the independent associations of muscular fitness (MF), cardiorespiratory fitness (CRF) and waist circumference (WC) with blood pressure (BP) levels over 2 years in children and adolescents. Methods: 1089 children (517 females) and 787 adolescents (378 females) with complete data on fitness, WC and BP (systolic [SBP] and diastolic [DBP]) were included. Upper MF was assessed through the hand grip strength test, and lower MF using the standing long jump test. The 20-m shuttle run test was used to assess CRF. WC was obtained following standardized methods. Different regression models were fitted by introducing fitness and WC at baseline and their changes as exposures and BP at follow-up and their changes as outcomes. Results: WC at baseline was positively and independently associated with each BP variable at followup in children and adolescents (beta = 0.094-0.260; p <= 0.05), and CRF was negatively associated with DBP in adolescents (beta =-0.096; p = 0.034). WC changes were associated with BP variables 2 years later in children (beta = 0.121-0.142; p < 0.01). In adolescents, changes in upper MF (beta =-0.116; p = 0.001) and WC (beta = 0.080-0.098; p < 0.05) were associated with SBP at follow-up. WC changes were independently associated with changes in each BP variable in children (beta = 0.111-0.145; all p < 0.05) and SBP changes in adolescents (beta = 0.103 to 0.117; all p < 0.01). Conclusions: WC, but neither MF nor CRF, is independently associated with BP and its changes over 2 years. The attainment or maintenance of optimal fatness levels in the pediatric population should be highly encouraged for the prevention of future hypertension. (C) 2021 Sports Medicine Australia. Published by Elsevier Ltd. All rights reserved.