Incidence rates of RA by 1987 ACR criteria per 100 000 population (95% CI)
| Group | Decade of RA incidence | Female | Male | Total |
| Overall | 1985–1994 | 48 (41 to 56) | 32 (25 to 40) | 40 (35 to 46) |
| 1995–2004 | 55 (48 to 63) | 30 (24 to 36) | 43 (38 to 48) | |
| 2005–2014 | 53 (47 to 59) | 29 (24 to 34) | 41 (37 to 45) | |
| RF positive | 1985–1994 | 33 (27 to 40) | 23 (17 to 30) | 28 (24 to 33) |
| 1995–2004 | 39 (33 to 45) | 19 (15 to 24) | 30 (26 to 33) | |
| 2005–2014 | 26 (22 to 30) | 15 (12 to 19) | 21 (18 to 24) | |
| RF negative | 1985–1994 | 15 (11 to 19) | 9 (5 to 12) | 12 (9 to 15) |
| 1995–2004 | 16 (13 to 20) | 10 (7 to 14) | 13 (11 to 16) | |
| 2005–2014 | 26 (22 to 31) | 14 (11 to 18) | 20 (18 to 23) |
ACR, American College of Rheumatology; RA, rheumatoid arthritis; RF, rheumatoid factor.