Baseline characteristics of patients with low BMD (Z≤−2 at any site)
| Variables | Low BMD (N=43) | No Low BMD (N=289) | p Value |
|---|---|---|---|
| Age, years (mean±SD) | 32.6 (7.2) | 34.0 (8.8) | 0.349 |
| Men (N, %) | 37 (86.1%) | 137 (47.4%) | 0<0.0001 |
| Menopause (N,%) | 0/6 (0.0%) | 7/152 (4.6%) | 1.000 |
| BMI, kg/m2 (mean±SD) | 23.0 (3.9) | 24.3 (4.2) | 0.024 |
| Disease duration, years (mean±SD) | 1.83 (1.55) | 1.58 (0.94) | 0.521 |
| Inflammatory bowel disease (N, %) | 4 (9.3%) | 8 (2.8%) | 0.056 |
| Tobacco use (N, %) | 20 (46.5%) | 94 (32.9%) | 0.080 |
| Alcohol excess (N, %) | 7 (16.3%) | 39 (13.7%) | 0.648 |
| HLA-B27 (N, %) | 31 (72.1%) | 174 (60.6%) | 0.148 |
| BAS-G, last week (mean±SD) | 4.95 (2.52) | 4.83 (2.53) | 0.848 |
| ASAS criteria (N, %) | 36 (83.7%) | 201 (69.6%) | 0.055 |
| BASDAI (mean±SD) | 4.34 (2.08) | 4.28 (2.04) | 0.929 |
| BASFI (mean±SD) | 3.00 (2.35) | 2.85 (2.33) | 0.657 |
| BASMI (mean±SD) | 2.28 (1.16) | 1.93 (1.08) | 0.050 |
| CRP, mg/ml (mean±SD) | 20.36 (27.03) | 8.14 (11.48) | 0.019 |
| CRP abnormal, ≥6 mg/dl (N, %) | 19 (54.3%) | 82 (37.6%) | 0.062 |
| ASDAS–CRP (mean±SD) | 3.06 (1.25) | 2.55 (0.92) | 0.041 |
| ESR, mm (mean±SD) | 25.00 (23.89) | 12.31 (13.92) | 0.0003 |
| NSAID use (N, %) | 39 (90.7%) | 269 (93.1%) | 0.532 |
| Rx sacroiliitis (N, %) | 17 (40.5%) | 77 (27.2%) | 0.077 |
| Inflammatory lesions on sacroiliac MRI (N, %) | 23 (56.1%) | 90 (33.8%) | 0.006 |
| Inflammatory lesions on spine MRI (N, %) | 19 (46.3%) | 44 (16.5%) | 0<0.0001 |
| Dorsal inflammatory lesions on spine (N, %) | 13 (31.7%) | 28 (10.7%) | 0.0003 |
| Lumbar inflammatory lesions on spine MRI (N, %) | 11 (26.8%) | 26 (9.8%) | 0.002 |
| Lumbar spine BMD (mean±SD) | 0.86 (0.10) | 1.11 (0.15) | 0<0.0001 |
| Lumbar spine Z score (mean±SD) | −2.38 (0.63) | −0.06 (1.10) | <0.0001 |
| Lumbar spine T score (mean±SD) | −2.37 (0.79) | −0.06 (1.08) | 0<0.0001 |
| Total hip BMD (mean±SD) | 0.87 (0.09) | 1.01 (0.13) | 0<0.0001 |
| Total hip Z score (mean±SD) | −1.24 (0.73) | 0.10 (0.99) | <0.0001 |
| Total hip T score (mean±SD) | −1.39 (0.77) | 0.02 (1.02) | 0<0.0001 |
| Femoral neck BMD (mean±SD) | 0.79 (0.10) | 0.94 (0.14) | 0<0.0001 |
| Femoral neck Z score (mean±SD) | −1.43 (0.75) | 0.01 (0.99) | <0.0001 |
| Femoral neck T score (mean±SD) | −1.71 (0.83) | −0.16 (1.08) | 0<0.0001 |
| Total lean mass, kg (mean±SD) | 51.4 (8.1) | 47.3 (10.6) | 0.022 |
| Total fat mass, kg (mean±SD) | 16.7 (8.3) | 20.5 (9.4) | 0.009 |
| % Fat mass (mean±SD) | 23.4 (8.6) | 28.4 (9.7) | 0.002 |
ASAS, Assessment of Spondyloarthritis International Society; ASDAS, ankylosing spondylitis disease activity score; BASDAI, Bath ankylosing spondylitis disease activity index; BASFI, Bath ankylosing spondylitis functional index; BAS-G, Bath ankylosing spondylitis global assessment; BASMI, Bath ankylosing spondylitis metrology index; BMD, bone mineral density; BMI, body mass index; CRP, C-reactive protein; ESR, erythrocyte sedimentation rate; NSAID, non-steroidal anti-inflammatory drug.