Descriptive characteristics of 957 identified incident IIM cases and matched controls
| IIM cases | Controls | |
| N | 957 | 9476 |
| Women, n (%) | 546 (57) | 5401 (57) |
| Age, mean (SD) | 59 (15) | 59 (15) |
| Education, n (%) | ||
| >12 years | 255 (27) | 2554 (27) |
| 10–12 years | 392 (41) | 3886 (41) |
| <9 years | 297 (31) | 2902 (31) |
| Missing | 13 (1) | 134 (1) |
| Diagnosis, n (%) | ||
| Dermatomyositis | 301 (31) | |
| Other IIM* | 656 (69) | |
| History of hospitalisation or outpatient visit indicating exposure†, n (%) | ||
| Infections | 125 (13) | 877 (9) |
| Respiratory tract disease | 92 (10) | 423 (4) |
| Years since last exposure†, mean (SD) | ||
| Infections | 3.4 (2.1) | 3.6 (2.3) |
| Respiratory tract disease | 3.0 (2.0) | 3.4 (2.2) |
*Other IIM includes polymyositis, inclusion body myositis and unspecified myositis
12-month latency period between exposure and outcome.