Matching variables for the three reference groups and characteristics of the study groups
| Cases n=1443 | Reference 1 (primary) n=5772 | Reference 2 n=5772 | Reference 3 n=5770 | |
|---|---|---|---|---|
| Number of matched references per case | 4 | 4 | 4* | |
| Matched on | ||||
| Sex | ✓ | ✓ | ✓ | |
| Age (±5 years) | ✓ | ✓ | ✓ | |
| Area of residence | ✓ | ✓ | ✓ | |
| Observation time | ✓ | ✓ | ✓ | |
| Educational level | ✓ | ✓ | ||
| Healthcare consultation in the year of case inclusion | ✓ | |||
| Women, n (%) | 784 (54) | 3136 (54) | 3136 (54) | 3136 (54) |
| Age, mean (SD) | 38 (14.6) | 38 (14.5) | 38 (14.7) | 38 (14.8) |
| Educational level, n (%) | ||||
| Low (≤9 years) | 246 (17.0) | 925 (16.0) | ||
| Medium (10–12 years) | 785 (54.4) | 2935 (50.8) | ||
| High (>12 years) | 397 (27.5) | 1791 (31.0) | ||
| Missing | 15 (1.0) | 121 (2.1) |
*For one case, only two references were identified.