Moderate-to-heavy smoking in women is potentially associated with compromised cortical porosity and stiffness at the distal radius

A Summary Though smokers have poor clinical outcomes after treatment for fractures, the skeletal effects of smoking are still debated. Our results showed that female smokers had 33% higher cortical bone porosity. Smoking targets cortical compartment microstructure and mechanics, and micron-scale variables are essential to better understand the specific effects of smoking. Purpose Smokers have poor outcomes in the clinic after treatment for fractures. However, skeletal effects of smoking are still debated. Inconsistencies in published data are likely due to macro-scale variables used to characterize bone differences due to smoking. Therefore, our goal was to characterize distal radius microstructure and macrostructure differences between smokers and non-smokers, and determine the degree to which smoking is associated with compartment-specific mechanical differences resulting from compromised cortical-trabecular microstructure. Methods Data were acquired from 46 female smokers (35 to 64 years old), and 45 age- and body mass-matched female nonsmokers. Distal radius microstructure and mechanical variables were determined from high-resolution peripheral quantitative computed tomography (HR-pQCT) images and multiscale finite element analysis. Distal radius macro-scale variables (bone volume, bone mineral content, volumetric bone mineral density [vBMD]) were determined from low-resolution images. Results Age- and body mass index-adjusted results showed that cortical porosity was 33% higher (p < 0.01), and that cortical vBMD and stiffness were 3% and 8% lower, respectively (p < 0.05), among smokers. We also observed unloading of the cortical compartment in smokers. There were no differences in the macro-scale variables. Average HR-pQCT-derived vBMD was 8% lower (p < 0.05) in smokers corresponding to 5 years of postmenopausal loss. Conclusion Skeletal effects of smoking become evident at the micron level through a structurally and mechanically compromised cortical compartment, which partially explains the inconsistent results observed at the macro-level, and the poor clinical outcomes. Smoking may also compound postmenopausal effects on bone potentially placing women having undergone menopause at a greater risk for fracture.