Prevalence and risk factors of low bone mineral density in spondyloarthritis and prevalence of vertebral fractures

BACKGROUND Investigate the prevalence and risk factors of low bone mineral density (BMD) in patients with axial spondyloarthritis as well as investigating the prevalence of vertebral fractures. METHODS Patients underwent BMD measurements with dual-energy X-ray absorptiometry (DXA) in the anterior-posterior lumbar spine, lateral spine and hip. We screened for vertebral fractures using vertebral fracture assessment, and then checked for syndesmophytes on the VFA images. Sociodemographic and clinical variables were collected. RESULTS A total of 89 patients (41,6% female) took part in the study with a mean age of 44 ± 14 years and disease duration 10.2 ± 10.6 years. According to World Health Organization (WHO) criteria, 48,3% of patients displayed osteopenia and 6,7% osteoporosis. In the subgroup of women who underwent measurement at all sites including the lateral spine, the prevalence of osteopenia was 39.3% in the anterior-posterior spine, 32.1% in the lateral spine, and 64.3% with all sites together. VFA led to the diagnosis of at least one vertebral fracture in 6.2% of patients. On VFA, syndesmophytes were found in 24.3% of patients. The variables associated in multivariate analyses with low BMD in different measurement sites were low body mass index (BMI), a high physician's global assessment score, a high Bath Ankylosing Spondylitis Functional Index (BASFI) score and female gender. CONCLUSION Our study found a high prevalence (around 50%) of low BMD in SpA. Conversely, the prevalence of osteoporosis (6.7% according to WHO criteria) and vertebral fractures (6.2%) was lower than generally reported in the literature. While lateral spine BMD measurement did little to improve the detection of osteopenia in women, the sample size was not large enough to enable us to draw definite conclusions.