Comparison of clinical characteristics between groups I and II
| Group I | Group II | |
| Initial visit (year range) | 1960–1965 | 1985–1990 |
| Institution | Osaka University Hospital | Shichikawa Arthritis Research Centre |
| Number of patients total | 566 | 366 |
| Male | 125 | 67 |
| Female | 441 | 299 |
| Ratio of males to females | 1:3.5 | 1:4.5 |
| Age at initial visit (y) : (mean (SD)) | 42.6 (14.3) | 54.5 (11.7)1-150 |
| Disease duration (y) total : (mean (SD)) | 4.9 (6.1) | 7.5 (8.2)1-150 |
| Male : (mean (SD)) | 4.9 (6.8) | 4.8 (4.5) |
| Female : (mean (SD)) | 4.9 (5.9) | 8.1 (8.7)1-150 |
| Age at onset (y) total : (mean (SD)) | 37.5 (14.1) | 46.9 (13.9)1-150 |
| Male : (mean (SD)) | 41.3 (15.3) | 54.0 (12.1)1-150 |
| Female : (mean (SD)) | 36.5 (13.6) | 45.3 (13.8)1-150 |
| Seropositivity (%) | 69.5 | 75.1 |
| Rheumatoid nodule positivity (%) | 9.9 | 12.3 |
| Rate of hip involvement (%) | 14.9 | 16.0 |
↵1-150 Significant difference (p<0.001) was observed between these two groups.