Univariate and multivariate logistic regression with WP as target variable (unimpaired WP=1, n=695)
| Predictors | Impaired WP (n=453) | Unimpaired WP (n=242) | βj (constant β0) | OR | 95% CI | χ2 | P value |
| Univariate logistic regression | |||||||
| General demographic characterisation | |||||||
| Age (years), mean±SD | 46.7±11.1 | 42.8±10.1 | −0.033 (0.846) | 0.968 | 0.953 to 0.982 | 19.87 | <0.001 |
| BMI, mean±SD | 28.5±14.0 | 27.0±6.8 | −0.015 (−0.204) | 0.985 | 0.965 to 1.005 | 3.05 | 0.146 |
| Male, % (n) | 54.3 (246) | 73.1 (177) | 0.850 (−1.174) | 2.340 | 1.665 to 3.289 | 25.29 | <0.001 |
| University education, % (n) | 23.0 (104) | 33.9 (82) | 0.561 (−0.786) | 1.752 | 1.242 to 2.471 | 10.10 | 0.001 |
| In a committed relationship, % (n) | 68.4 (310) | 65.7 (159) | −0.124 (−0.544) | 0.884 | 0.635 to 1.231 | 0.53 | 0.464 |
| Work characterisation | |||||||
| Full time employment, % (n) | 56.5 (256) | 83.5 (202) | 1.357 (−1.594) | 3.886 | 2.640 to 5.721 | 54.68 | <0.001 |
| Short-term absenteeism (WPAI–axSpA), mean±SD | 17.9±32.1 | 0 | |||||
| Short-term presenteeism (WPAI–axSpA), mean±SD | 48.6±21.0 | 9.6±8.3 | |||||
| Clinical characterisation | |||||||
| Disease duration (years) | 12.7±11.3 | 12.4±10.2 | −0.002 (−0.605) | 0.998 | 0.984 to 1.013 | 0.06 | 0.813 |
| Biological treatment, % (n) | 50.8 (230) | 55.4 (134) | −0.126 (−0.578) | 0.882 | 0.639 to 1.216 | 0.59 | 0.442 |
| PROs | |||||||
| ASAS-HI score, mean±SD | 8.0±3.3 | 3.7±3.0 | −0.421 (1.777) | 0.657 | 0.614 to 0.702 | 238.65 | <0.001 |
| BASDAI score, mean±SD | 4.8±1.9 | 2.1±1.6 | −0.910 (2.379) | 0.402 | 0.351 to 0.462 | 305.32 | <0.001 |
| BASDAI score ≥4, % (n) | 65.3 (296) | 12.0 (29) | −2.628 (0.305) | 0.072 | 0.049 to 0.111 | 198.48 | <0.001 |
| BASDAI fatigue score, mean±SD | 5.8±2.1 | 2.8±2.1 | −0.619 (1.992) | 0.539 | 0.489 to 0.593 | 247.71 | <0.001 |
| BASDAI duration morning stiffness score, mean±SD | 3.5±2.4 | 1.6±1.8 | −0.487 (0.529) | 0.615 | 0.553 to 0.683 | 120.75 | <0.001 |
| BASFI, mean±SD | 4.2±2.3 | 1.5±1.5 | −0.711 (1.262) | 0.491 | 0.437 to 0.552 | 245.42 | <0.001 |
| Multivariate logistic regression | |||||||
| Constant | 3.652 | ||||||
| ASAS-HI score | −0.144 | 0.866 | 0.792 to 0.947 | 0.002 | |||
| BASDAI score | −0.553 | 0.576 | 0.426 to 0.778 | <0.001 | |||
| BASDAI score ≥4 | 0.477 | 1.563 | 0.723 to 3.380 | 0.256 | |||
| BASDAI fatigue score | −0.118 | 0.888 | 0.759 to 1.039 | 0.139 | |||
| BASDAI duration morning stiffness score | −0.030 | 0.971 | 0.848 to 1.111 | 0.665 | |||
| BASFI score | −0.204 | 0.816 | 0.688 to 0.966 | 0.018 | |||
| Full model | 350.81 | <0.001 | |||||
*For univariate models, df=1; for the multivariate full model, df=14.
ASAS-HI, Assessment of SpondyloArthritis International Society–Health Index; axSpA, axial spondyloarthritis; BASDAI, Bath Ankylosing Spondylitis Disease Activity Index; BASFI, Bath Ankylosing Spondylitis Functional Index; BMI, body mass index; PRO, patient-reported outcome; WP, work participation; WPAI, Work Productivity and Activity Impairment Questionnaire; βj, regression coefficient.