Participants’ basic demographic and clinical characteristics, including the number of biological children per men.
| All patients | IA diagnosed at age <30 years | IA diagnosed at age 31-40 years | IA diagnosed at age >41 years | |
| Total, n (%) | 628 | 137 (21.82) | 149 (23.73) | 342 (54.46) |
| Age, mean (SD) | 57.17 (9.98) | 53.01 (9.96) | 52.76 (7.35) | 61.06 (9.47) |
| Diagnosis, n (%) | ||||
| •iRA | 297 (47.29) | 42 (30.66) | 67 (44.97) | 188 (55.32) |
| •AJIA | 10 (1.59) | 10 (6.25) | 0 (0) | 0 (0) |
| •ISpA (incl. PsA) | 320 (50.96) | 90 (65.69) | 83 (55.70) | 147 (42.98) |
| Age at diagnosis, mean (SD) | 41.29 (13.08) | 26.27 (9.15) | 36.99 (5.66) | 49.98 (9.70) |
| Disease duration, mean (SD) | 15.89 (11.88) | 26.48 (12.57) | 15.70 (8.52) | 11.30 (9.87) |
| Number of biological children, mean (95% CI) | 1.71 (1.60-1.81) | 1.39 (1.15-1.63)a,b | 1.60 (1.38-1.82)a | 1.88 (1.75 -2.01) |
a p< 0.05 compared to those diagnosed age >41 years
b p< 0.05 compared to those diagnosed age >31-40 years