| Mean age (years) | 45 | 45 |
| HLA B27 positive | 55% | 78% |
| Under TNF-α inhibitor treatment | 78% | 68% |
| Under DMARDs* therapy | 10% | 7% |
| Under NSAID** therapy | 16% | 22% |
| Inflammatory bowel disease (IBD) | 6% | 2% |
| Past or current corticosteroid therapy | 20% | 27% |
| Smoking | 37% (18% unknown) | 46% (10% unknown) |
| Antiosteoporotic treatment | 18% | 5% |
| Ca & Vit D supplementation | 33% | 17% |
| Mean BMI (kg/m2) | 25.6 | 26.3 |
| Mean hip BMD T-score | −0.87±1.08 | −1.56±0.88 |
| Mean spine BMD T-score | −0.82±1.77 | −1.16±1.82 |
| Mean spine TBS T-score | −0.48±1.17 | −0.92±1.49 |
| BASMI (subset Sofia only) | 3.22±1.9 | 4.81±1.9 |
| BASDAI (subset Sofia only) | 4.31±2.5 | 4.28±2.2 |
| BASFI (subset Sofia only) | 4.21±2.5 | 4.26±2.3 |
| ASDAS-CRP (subset Sofia only) | 2.62±1.3 | 2.79±1.0 |