Height-adjusted lean body mass and its associations with physical activity and kidney function in pediatric kidney transplantation.

Background: Although LBM is positively associated with health outcomes, studies assessing determinants for the accrual of ht-LBM, such as physical activity, are limited. This study aimed to assess ht-LBM levels in pediatric kidney transplant recipients and test its association with baseline and contemporaneous variables, including physical activity.

Methods: A retrospective cross-sectional review was performed on 46 pediatric kidney transplant recipients, and a longitudinal review was performed on a subset of recipients with serial post-transplant (n = 21) and pre/post-transplant (n = 11) ht-LBM measurements. Ht-LBM measurements were obtained using DXA scans.

Results: This cohort was 16.0 (IQR 12.3, 17.7) years old, 56.5% male and 46 ± 45 months post-transplant with a mean ht-LBM of 15.1 ± 2.5 kg/m . A median ht-LBM increase of 1.6 kg/m (IQR - 0.1, 2.6 kg/m ; p < .01) was observed, over 29.2 ± 12.0 months from the earliest post-transplant scan obtained at 46 ± 25 months post-transplant until the most recent post-transplant scan. A 1.7 ± 1.4 kg/m (p < .01) increase was observed between pre- and post-transplant DXA scans which were taken at 12 ± 11 months pre-transplant and 13 ± 6 months post-transplant, respectively. In separate adjusted models, lower physical activity questionnaire scores (n = 17, beta = 1.55, p = .02), faster rate of estimated glomerular filtration rate decline (beta = 0.05, p < .048) adjusted for annualized change in BSA, and younger age at scan (beta = 0.32, p < .01) were each significant predictors of lower ht-LBM.

Conclusions: Physical activity and kidney function may influence ht-LBM in the pediatric kidney transplant population.