Cardiorespiratory fitness in young adults with a history of renal transplantation in childhood

Limited knowledge exists on cardiorespiratory fitness (CR fitness) in adults having a renal transplant (Rtx) during childhood. Our aim was to assess CR fitness (V0(2peak)) with a maximal treadmill test in former Rtx children reaching adulthood (ped-tx, n = 31), compared to patients Rtx as adults (adult-tx, n = 17) and healthy controls (HC, n = 36). Median age was 26.9 (19-41), 28.6 (23.5-34) and 33.5 (20-42) years, respectively. Median time since first Rtx was 18.1 (7-29) and 3.7 (1.2-12.6) years. Body composition was measured by dual-energy X-ray absorptiometry (DXA). V0(2peak) was median 37.9 (12.5-56.3), 40.8 (26.5-57.5), and 44.4 (29.5-65.6) ml kg (-1)min (-1) in the ped-tx, adult-tx, and HC, respectively. Ped-tx had significantly lower V0(2peak) compared to HC (p = 0.01). Adult-tx had higher exercise capacity (test duration) compared to ped-tx (median 10.5 (7.5-16) and 9 (6-14) min, respectively (p = 0.016). In multiple linear regression analysis, test duration, fat-free mass (FFM, kg) and Hgb (g/dl) were significant predictors of V0(2peak) explaining 86% of its variance. There was no significant difference between ped-tx and adult-tx in V0(2peak.) CR fitness depicts long-term health outcome in Rtx patients both in regard to physical functioning and is a plausible indirect marker of CV health.