Bone mineral density in ankylosing spondylitis: Relation to disease activity, functional capacity, spinal mobility and radiological damage

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Aim of the workTo assess the bone mineral density (BMD) in Ankylosing Spondylitis (AS) patients and to investigate its relation to disease activity, functional capacity, spinal mobility and radiological damage. Patients and methodsThirty male AS patients (mean age 27.9 ± 6.2 and disease duration 4.2 ± 3.6 years) and thirty age-matched healthy controls were studied. Patients were assessed using the Bath Ankylosing Spondylitis Disease Activity Index (BASDAI), the Bath Ankylosing Spondylitis Functional Index (BASFI), the Bath Ankylosing Spondylitis Metrology Index (BASMI) and the modified Stoke Ankylosing Spondylitis Spinal Score (mSASSS) to quantify radiological damage. BMD of the lumbar spine and femoral neck were assessed by Dual Energy X ray Absorptiometry (DEXA). ResultsPatients had a lower BMD of the lumbar spine (1.13 ± 0.14 versus 1.22 ± 0.09 g/cm2, p = 0.007) and femoral neck (0.89 ± 0.1 versus 1.05 ± 0.13 g/cm2, p = 0.001) than controls. BMD of the lumbar spine was negatively correlated with the erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), BASDAI, BASFI, BASMI and mSASSS (r = -0.6,-0.4, −0.5, −0.4, −0.5, −0.6; p = 0.001, 0.003, 0.01, 0.01, 0.004, 0.001, respectively) while BMD of the femoral neck was correlated negatively with the ESR,CRP, mSASSS (r = -0.5,-0.4,-0.5, p = 0.001, 0.004, 0.01) and positively with the modified Schöber test (r = 0.41, p = 0.02). On multiple regression analysis, the modified Schöber test, ESR and CRP were independent predictors of the BMD of the femoral neck (β = 0.45,-1.12, 0.58; p = 0.048, 0.02, 0.03, respectively). ConclusionBMD is reduced in AS patients and correlates with disease activity, functional capacity, spinal mobility and radiological damage.