Incidence rate in the study sample according to drug exposure
| Incident rheumatoid arthritis | Person-years | Exposure periods | Incident rate *1000/yr (95% CI) | |
| Tamoxifen | 26 | 8650.2 | 3371 | 3.01 (1.96 to 4.40) |
| Aromatase inhibitors | 87 | 17 455.7 | 6815 | 4.98 (3.99 to 6.15) |
| Anastrozole | 50 | 9457.8 | 3170 | 5.29 (3.92 to 6.97) |
| Letrozole | 30 | 6626.6 | 2785 | 4.53 (3.05 to 6.46) |
| Exemestane | 7 | 1371.3 | 860 | 5.10 (2.05 to 10.5) |