Table 2.
Descriptive statistics of rheumatoid arthritis (RA) cases ascertained through the Swedish National Patient Register, their matched controls and index individuals’ first-degree relatives
| Seropositive RA
|
Seronegative RA
|
|||
|---|---|---|---|---|
| Index individuals | Cases | Controls | Cases | Controls |
| N | 41 061 | 195 095 | 13 454 | 63 395 |
| Men, % | 27.7 | 27.3 | 29.4 | 29.3 |
| Age at inclusion, years, median (1st–3rd quartile) | 62 (52–72) | 61 (52–71) | 63 (50–76) | 62 (49–74) |
| Their first-degree relatives | ||||
| N | 153 566 | 742 482 | 49 575 | 238 059 |
| Men, % | 51.0 | 51.6 | 51.2 | 51.8 |
| Birth year, median (1st–3rd quartile) | 1966 (1955–1977) | 1967 (1957–1978) | 1965 (1954–1978) | 1966 (1955–1979) |
| Diseases among the first-degree relatives | ||||
| Seropositive RA | 3447 (2.24%) | 4312 (0.58%) | 689 (1.39%) | 1360 (0.57%) |
| Seronegative RA | 720 (0.47%) | 1407 (0.19%) | 257 (0.52%) | 452 (0.19%) |
| Juvenile idiopathic arthritis | 120 (0.08%) | 159 (0.02%) | 68 (0.14%) | 57 (0.02%) |
| Other inflammatory arthritis | 1319 (0.86%) | 3979 (0.54%) | 418 (0.84%) | 1296 (0.54%) |
| Spondyloarthropathies | 4485 (2.92%) | 17 983 (2.42%) | 1586 (3.20%) | 5808 (2.44%) |
| Psoriasis/psoriatic arthritis | 2722 (1.77%) | 10 663(1.44%) | 1006 (2.03%) | 3404 (1.43%) |
| Lupus | 273 (0.18%) | 686 (0.09%) | 73 (0.15%) | 209 (0.09%) |
| Connective tissue diseases | 506 (0.33%) | 1194 (0.16%) | 138 (0.28%) | 380 (0.16%) |
| Arthralgia | 2994 (1.95%) | 11 781 (1.59%) | 972 (1.96%) | 3753 (1.58%) |
| Osteoarthritis | 8293 (5.40%) | 38 972 (5.25%) | 2797 (5.64%) | 12 565 (5.28%) |