Obesity and osteoporosis are two important and growing public health problems worldwide. Body mass index (BMI) has been found to be inversely related to the risk of osteoporotic fracture. We aimed to assess the association of BMI with thoracic vertebral bone mineral density (BMD) measured from a quantitative computed tomography (QCT).

We retrospectively evaluated the data from 15,758 consecutive patients (5675 females and 10,083 males) between age 20–90 years, who underwent Coronary Artery Calcium (CAC) scoring. Quantitative data analyses of thoracic trabecular BMD (mg/cm³) was performed with a phantom system or phantomless using validated software. The gender-specific subgroup was divided based on age (<45, 45–55, 55–65, >65 yrs in females; <40,40–60,>60 yrs in Males) and weight by BMI (kg/m²) as < 25 (normal or low weight), >25 - <30 (overweight) and >30 (obesity). Analysis of variance (ANOVA) and Scheffe's post hoc procedure tested the association of body weight/BMI on BMD. A significant positive association between the body weight and BMD existed in obese population in elder groups in both genders (p < 0.05). There was no significant difference in BMD in 40–60 years in men and <55 years in women with normal or low weight compared to overweight or obese cohorts.

We concluded that the effect of weight on BMD is age-specific and the BMD should be monitored routinely with a cardiac CT scan in the senile population.