Smoking Is Associated with Lower Bone Mineral Density and Reduced Cortical Thickness in Young Men

Context: Smoking has previously been associated with reduced areal bone mineral density (aBMD) in elderly subjects, but the association remains controversial in adolescents. Objective: The aim of this study was to determine whether smoking was associated with aBMD or volumetric BMD (vBMD) and bone size in young men. Design and Setting: aBMD was measured using dual x-ray absorptiometry. vBMD and bone size were measured using peripheral quantitative computerized tomography (pQCT). Smoking habits were assessed using questionnaires. Levels of sex steroids, PTH, and 25-OH-vitamin D were measured in serum. Participants: The population-based Gothenburg Osteoporosis and Obesity Determinants (GOOD) study includes 1068 young men, age 18.9 ± 0.6 yr (mean ± sd). Main Outcome Measure: The main outcome measure was smoking as predictor of bone parameters and serum sex hormone levels. Results: Of the study subjects, 8.7% smoked daily. Bone parameters were compared between smokers and nonsmokers. Smokers had significantly lower aBMD (dual x-ray absorptiometry) of the total body (crude: −2.1%; adjusted for age, height, weight, calcium intake, and physical activity: −1.8%), lumbar spine (crude: −4.3%; adjusted: −3.3%), and trochanter (crude: −6.6%; adjusted: −5.0%) than nonsmokers. Using peripheral quantitative computerized tomography, we found that smokers had lower cortical thickness of both the radius (crude: −2.8%; adjusted: −2.9%) and tibia (crude: −4.5%; adjusted: −4.0%) than the nonsmokers, whereas no difference was seen for cortical vBMD. Smokers had higher serum levels of total and free testosterone and lower 25-OH-vitamin D than nonsmokers. Adjustment for testosterone and/or 25-OH-vitamin D levels did not alter the associations between smoking and bone parameters. Conclusions: We demonstrate that smoking was associated with lower aBMD and reduced cortical thickness in young men.