Background The disease process of ankylosing spondylitis (AS) is characterized by chronic inflammation. Osteoporosis is now known to be associated with chronic inflammation. Bone loss occurs early in AS increasing the risk of fracture, and is related mainly to the inflammatory process. This study aims to determine the relationship between AS and osteoporosis.
Objectives To determine the prevalence and risk factors of low bone mineral density (BMD) in a local Hong Kong Chinese cohort of ankylosing spondylitis (AS) patients. Dual X-ray absortiometry (DXA) scan at different sites were compared and evaluated.
Methods Ninety-two patients with AS were enrolled in this study. Clinical, demographic and radiological data were collected. Erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), Bath AS Disease Activity Index (BASDAI), Bath AS Functional Index (BASFI), Ankylosing Spondylitis Disease Activity Score (ASDAS), Patient and Physician global scores, Health Assessment Questionnaire (HAQ) and Bath AS Metrology Index (BASMI) were evaluated. BMD at the lumbar spine via antero-posterior (AP) and lateral projections, neck of femur (NOF) and total hip were measured.
Results Low BMD was found in half of the 92 Chinese AS patients. Factors associated with low BMD were BASDAI, BASMI, post-menopausal status, body mass index (BMI), alcohol use and family history of AS. Multiple logistic regression analysis by backward selection revealed that BASDAI (odds ratio (OR) 1.03, 95% confidence interval (CI)1.00–1.06; p =0.031), post-menopausal status (OR 6.11, 95% CI 1.07–34.81; p =0.041), BMI (OR 0.81, 95% CI 0.71–0.93; p =0.003) and alcohol use (OR 4.79, 95% CI 1.49–15.38; p =0.008) were significantly associated with low BMD. Total hip BMD was more sensitive than AP lumbar BMD in detecting low BMD in AS.
Conclusions Low BMD in AS is not uncommon and often underdiagnosed. BASDAI, post-menopausal status, alcohol use and BMI were independently associated with low BMD in this study.
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Disclosure of Interest None declared