Excess body fat is associated with higher risk of vertebral deformities in older women but not in men: a cross-sectional study

Summary: Thinness is a risk factor for fractures, but the effect of obesity on fracture risk is less clear. We found an association between measures of obesity and prevalence and number of vertebral deformities in women but not in men, in a cross-sectional study of 1,011 participants aged 50-80 years.

Introduction: Low body weight is well recognised as a risk factor for fractures, but the association between overweight and fracture risk is less well described. This cross-sectional study describes the association between measures of obesity and vertebral deformities in 1,011 male and female participants in the Tasmanian Older Adult Cohort study.

Methods: Vertebral deformities (anterior wedging) of T4-CL4 were determined by morphometric dual-emission X-ray absorptiometry. Body fat was assessed as weight, body mass index (BMI), waist-hip ratio (WHR), waist circumference and DXA measures of trunk fat (in percent) and total fat mass.

Results: The mean age of participants was 63±7 years, and mean BMI was 28±5. Prevalent thoracic vertebral deformities were associated with increasing weight [standardised β (Sβ) 0.29, p=0.003], BMI (Sβ 0.33, p<0.001), trunk fat (Sβ 0.20, p=0.03), waist circumference (Sβ 0.19, p=0.03) and fat mass (Sβ 0.23, p=0.03), but not the WHR in women, and only with decreasing total fat mass in men. In addition, the number of vertebral deformities increased as weight, BMI or fat mass increased in women (all p<0.05) but decreased with increasing total fat mass in men. Associations between fat mass and vertebral deformities were mainly linear, but there was some evidence of a threshold effect in women with a BMI ≥35.

Conclusions: There is a deleterious association between increasing amounts of body fat in women but not in men and the prevalence and number of vertebral deformities, which may reflect loading of the thoracic spine.