Table 1 Basic characteristics of cases and controls
| Â | Controls | JIA | Â |
|---|---|---|---|
| Â | n (%) | n (%) | p |
No. of subjects | 16,369 | 102 | Â |
Sex | |||
 Boys | 8453 (52%) | 33 (32%) | < 0.001 |
 Girls | 7814 (48%) | 69 (68%) | |
Gestational age, weeks (SD) | 39.7 (2.4) | 39.6 (2.0) | 0.511 |
Season of birth | |||
 Winter (December–February) | 3840 (24%) | 18 (18%) | 0.155 |
 Spring (March–May) | 4607 (28%) | 34 (33%) | 0.268 |
 Summer (June–August) | 4270 (26%) | 26 (25%) | 0.854 |
 Autumn (September–November) | 3523 (22%) | 24 (24%) | 0.654 |
Category at Onset (ILAR) (n) | |||
 Systemic Arthritis |  | 7 (7%) |  |
 Oligoarthritis |  | 25 (25%) |  |
  Persistent oligoarthritis |  | 19 (19%) |  |
  Extended oligoarthritis |  | 6 (6%) |  |
 Polyarthritis (Rheumatoid Factor Negative) |  | 16 (16%) |  |
 Polyarthritis (Rheumatoid Factor Positive) |  | 4 (4%) |  |
 Psoriatic Arthritis |  | 11 (11%) |  |
 Enthesitis Related Arthritis |  | 16 (16%) |  |
 Undifferentiated Arthritis |  | 23 (23%) |  |