Bone Micro-Architecture and Physical Activity in Children with Type 1 Diabetes

Abstract

INTRODUCTION: Individuals with type 1 diabetes (DM1) have a 14-40% greater risk of fractures at all ages. The etiology of greater fracture risk is not known, but possibly related to alterations in bone size, density and micro architecture. Childhood and early adolescent growth years are the best time to optimize the effects of physical activity (PA) on bone development. My primary objective was to compare bone size, density, and micro-architecture at the distal radius and tibia between children with DM1 and typically-developing children (TDC). My secondary objective was to explore the role of daily minutes of moderate-to-vigorous PA (MVPA), vigorous PA (VPA), and daily impacts on bone outcomes that differed between children with DM1 and TDC. METHODS: Using a cross-sectional design, I analyzed data from 68 children (mean age 11.3, SD 1.9y), categorized into DM1 group (N=21) and TDC group (N=47). High-resolution peripheral quantitative computed tomography (HR-pQCT) measured bone size, density, and micro-architecture at dominant side distal radius and tibia and pQCT measured forearm and lower leg muscle area. Triaxial accelerometers recorded daily minutes of MVPA, VPA, and daily impact counts ≥3.9g. Site-specific MANCOVAs and pairwise comparisons (Bonferroni) assessed group differences (Pillai’s trace) and β-coefficients assessed role of PA. Base models were adjusted for sex, maturity, site-specific muscle area, and BMI z-score. Significance set at p<0.05. RESULTS: Bone properties differed between groups at the radius (F(18,42)=7.59, p<0.001) and tibia (F(18,42)=2.83, p=0.003). DM1 had lower total area, greater total and cortical densities, greater cortical thickness, lower cortical porosity, pore volume, pore diameter, trabecular area and number, and greater trabecular separation at radius. DM1 had lower cortical porosity, pore volume, pore diameter at tibia. VPA was an independent predictor of cortical pore diameter at the radius (Std. β=-0.18). Significance p<0.05. CONCLUSIONS: Children with DM1 had deficits in total bone size, greater total and cortical densities, and alterations in cortical and trabecular micro-architecture at the radius, as well as alterations in cortical micro-architecture at the tibia. VPA independently predicted cortical pore diameter at the radius.