Objectives To assess the 2-year bone mineral density (BMD) changes at lumbar spine and hip in a large cohort of patients with early inflammatory back pain (IBP) suggestive of axial Spondyloarthritis (SpA), and to assess determinants of bone loss.
Methods of the 708 patients of the DESIR cohort (IBP of less than 3 years duration suggestive of axial SpA), 265 (54% males, mean age 34.4 years) had BMD measurements at baseline and 2 years. Low BMD was defined as Z score ≤-2 (at at least one site) and significant bone loss was defined by a decrease in BMD≥0.03g/cm². Clinical, biological (erythrocyte sedimentation rate ESR and C reactive protein CRP, bone formation inhibitors markers (sclerostin and DKK-1 serum levels)), imaging (X-rays, spine and sacroiliac joints MRI) parameters and therapies were assessed. AntiTNF users were defined as those who received antiTNF at 2 years. The dependant variable of this study was the bone loss (decrease in BMD≥ 0.03 g/cm2) at either lumbar spine or hip site. Independant variables included both the ones collected at baseline (age, gender, BMI, BASDAI, ADSAS CRP, ESR, CRP, HLA B27, NSAIDS use, continuous use of NSAIDS, X-rays sacroiliitis, bone marrow oedema on sacroiliac or spine MRI, lean and fat masses, sclerostin and DKK-1) and the ones collected at the 2-year visit (age, gender, BMI, BASDAI, ADSAS CRP, ESR, CRP, NSAIDS use, continuous use of NSAIDS, use and duration of antiTNF, syndesmophytes, bone marrow oedema on sacroiliac or spine MRI, lean and fat masses). Parameters were tested in univariate and multivariate analyses; accuracy of models was measured by the area under the curve (AUC).
Results Thirty nine patients (14.7%) patients had low BMD at baseline. 2-year BMD significantly changed from baseline at lumbar spine (+1.3 (6.4) %, p=0.02) and total hip (-0.3 (4.0) %, p=0.02). 95 patients (35.8%) had a 2-year significant bone loss (at lumbar spine or hip), 59 (22.4%) at lumbar spine and 46 (18.0%) at total hip. 187 (70.6%) and 134 (50.6%) had continuous use of NSAIDS at baseline, and at 2 years; 89 (33.6%) received anti-TNF at 2 years (mean duration 5.7 (9.1) months). In multivariate analysis, continuous use of NSAIDS at 2 years (OR=0.20 (0.06–0.63), p=0.006) and 2-years BMI (OR= 0.49 (0.30 – 0.78), p=0.003) had a protective effect on hip bone loss, while baseline BMI was associated with bone loss (OR= 1.58 (1.09 – 2.30), p=0.016) (AUC= 0.782). In patients without anti-TNF treatments at 2 years (n=176): continuous use of NSAIDS at 2 years (OR= 0.17 (0.03 – 0.83), p= 0.028) and 2-years BMI (OR= 0.66 (0.48 – 0.90), p=0.008) had protective effects on bone loss; in contrast 2-year BASDAI was the single parameter associated with hip bone loss (OR= 4.5 (1.03 – 20.0), p=0.04) (AUC=0.844). Significant 2-year lumbar spine bone loss was associated in multivariate analysis with age (OR=1.06 (1.00 – 1.12), p=0.04) and 2-year ADSAS CRP (OR= 1.72 (1.02 – 2.91), p=0.043) (AUC=0.708).
Conclusions 35% of young adults with early IBP suggestive of SpA have significant bone loss over 2 years. Continuous use of NSAIDS and high BMI are protective factors of hip bone loss in patients with or without antiTNF
Disclosure of Interest None Declared
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