Smoking is associated with lower bone mineral density and reduced cortical thickness in young men.

Abstract

Smoking has previously been associated with reduced areal bone mineral density (aBMD) in elderly subjects, but the association remains controversial in adolescents. The aim of this study was to determine whether smoking was associated with aBMD or volumetric BMD (vBMD) and bone size in young men. 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. The population-based Gothenburg Osteoporosis and Obesity Determinants (GOOD) study includes 1068 young men, age 18.9 +/- 0.6 yr (mean +/- SD). The main outcome measure was smoking as predictor of bone parameters and serum sex hormone levels. 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. We demonstrate that smoking was associated with lower aBMD and reduced cortical thickness in young men.