Variable | AS(n=214) | Controls (n=470) | P values* |
Age, years | 48.3 (10.4) | 39.3 (12.7) | <0.01 |
Male, n (%) | 127 (59.3) | 323 (68.7) | 0.02 |
Education, n (%) | <0.01† | ||
Primary school | 2 (0.9) | 0 (0.0) | |
Lower (professional) education | 36 (16.8) | 30 (6.4) | |
Secondary education | 107 (50.0) | 207 (44.0) | |
Higher education/university | 69 (32.2) | 233 (49.6) | |
Current smoker, n (%) | 43 (20.1) | 90 (19.2) | 0.78 |
Alcohol use (yes), n (%) | 168 (78.5) | 389 (82.8) | 0.18 |
BMI, kg/m2 | 26.3 (4.4) | 25.3 (4.3) | <0.01 |
Currently employed, n (%) | 139 (65.0) | 393 (83.6) | <0.01 |
Work disability, n (%) | 58 (27.1) | 17 (3.6) | <0.01 |
Annual income, n (%) | <0.01 | ||
≤€20 000 | 64 (29.9) | 44 (11.3) | |
>€20 000 and ≤€40 000 | 65 (30.4) | 113 (29.0) | |
>€40 000 and ≤€60 000 | 39 (18.2) | 123 (31.5) | |
>€60 000 | 46 (21.5) | 110 (28.2) | |
Symptom duration, years | 21.4 (11.2) | n/a | n/a |
Time since diagnosis, years | 15.5 (10.7) | n/a | n/a |
Current medication use, n (%) | n/a | ||
NSAID | 117 (54.7) | n/a | |
Anti-TNF | 119 (55.6) | n/a | |
SCQ (0-39)‡ | 2.7 (4.1) | 1.0 (1.7) | <0.01 |
History of psoriasis, n (%) | 18 (8.4) | n/a | n/a |
History of uveitis, n (%) | 38 (17.8) | n/a | n/a |
History of IBD, n (%) | 31 (14.5) | n/a | n/a |
BASDAI | 4.3 (2.2) | n/a | n/a |
BASFI | 4.1 (2.5) | n/a | n/a |
SF-36PCS (0–100) | 39.5 (10.6) | 53.9 (8.4) | <0.01 |
SF-36MCS (0–100) | 49.2 (12.8) | 49.4 (11.7) | 0.32 |
Mastery (7–28) | 20.8 (4.0) | 22.4 (3.9) | <0.01 |
Values expressed as mean (SD) unless otherwise stated.
* Two-tailed patients versus controls. Continuous data: independent t-tests for normally distributed variables and Mann-Whitney tests for non-normally distributed variables. Categorical data: χ² tests and Fisher’s exact tests (latter for small samples, expected count<5).
† Result of χ² test, 4×2 table. Posthoc test for difference in level of education (high vs other) between groups was significant (p<0.001).
‡ Modified SCQ, excluding questions on back pain, chronic rheumatic disease and osteoarthritis.
AS, ankylosing spondylitis; BASDAI, Bath Ankylosing Spondylitis Disease Activity Index; BASFI, Bath Ankylosing Spondylitis Functional Index; BMI, body mass index; IBD, inflammatory bowel disease; n/a, not applicable; NSAID, non-steroidal anti-inflammatory drug; SCQ, Self-Administered Comorbidity Questionnaire; SF-36PCS, Short Form (36) Physical Component Summary; SF-36MCS, Short Form (36) Mental Component Summary; TNF, tumour necrosis factor.