How does obesity influence the risk of vertebral fracture? Findings from the UK Biobank participants

Obesity and osteoporotic-related fractures are two common public health problems, although it is unclear how obesity affects the risk of vertebral fractures. The purpose of this study was to examine the association between different measures of obesity and the risk of vertebral fracture, and to establish the various clinical factors that can predict such risk. We analysed the data obtained from 502,543 participants in the UK Biobank (229,138 men and 273,405 women) who were aged 40-69 years. Imaging information was available in a subset of this cohort (5,189 participants, 2,473 men and 2,716 women). We further examined how bone mineral density (BMD) and geometry of the vertebrae were related to body fat measures. It was shown that a larger waist circumference, but not body mass index (BMI), was associated with an increase in fracture risk in men, but in women, neither BMI nor waist circumference affected the risk. Trunk fat mass, visceral adipose tissue (VAT) mass and limb fat mass were negatively associated with vertebral body BMD and geometry in men and women. BMD and geometry are related to the vertebral strength, but may not be directly related to the risk of fractures which are also influenced by other factors. The binary logistic regression equation established in this study may be useful to clinicians for prediction of vertebral fracture risks, and may provide further information to supplement FRAX which assesses general fracture risks.