Smoking is associated with impaired bone mass development in young adult men: a 5-year longitudinal study.

It has previously been shown that smoking is associated with reduced bone mass and increased fracture risk, but no longitudinal studies have been published investigating altered smoking behavior at the time of bone mass acquisition. The aim of this study was to investigate the development of bone density and geometry according to alterations in smoking behavior in a 5-year, longitudinal, population-based study of 833 young men, age 18 to 20 years (baseline). Furthermore, we aimed to examine the cross-sectional, associations between current smoking and parameters of trabecular microarchitecture of the radius and tibia, using high-resolution peripheral quantitative computed tomography (HR-pQCT), in young men aged 23 to 25 years (5-year follow-up). Men who had started to smoke since baseline had considerably smaller increases in areal bone mineral density (aBMD) at the total body (mean ± SD, 0.020 ± 0.047 mg/cm(2) versus 0.043 ± 0.040 mg/cm(2) , p < 0.01) and lumbar spine (0.027 ± 0.062 mg/cm(2) versus 0.052 ± 0.065 mg/cm(2) , p = 0.04), and substantially greater decreases in aBMD at the total hip (-0.055 ± 0.058 mg/cm(2) versus -0.021 ± 0.062 mg/cm(2) , p < 0.01) and femoral neck (-0.077 ± 0.059 mg/cm(2) versus -0.042 ± 0.070 mg/cm(2) , p < 0.01) than men who were nonsmokers at both the baseline and follow-up visits. At the tibia, subjects who had started to smoke had a smaller increment of the cortical cross-sectional area (CSA) than nonsmokers (8.1 ± 4.3 mm(2) versus 11.5 ± 8.9 mm(2) , p = 0.03), and a larger decrement of trabecular volumetric BMD (vBMD) than nonsmokers (-13.9 ± 20.5 mg/mm(3) versus -4.1 ± 13.9 mg/mm(3) , p < 0.001). In the cross-sectional analysis at follow-up (23-25 years of age), smokers had significantly lower trabecular vBMD at the tibia (7.0%, p < 0.01) due to reduced trabecular thickness (8.9%, p < 0.001), as assessed using HR-pQCT, than nonsmokers. In conclusion, this study is the first to report that men who start to smoke in young adulthood have poorer development of their aBMD at clinically important sites such as the spine and hip than nonsmokers, possibly due to augmented loss of trabecular density and impaired growth of cortical cross-sectional area.