Table 3

Baseline characteristics of patients with low BMD (Z≤−2 at any site)

VariablesLow 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.