Regional incidence rates (95% confidence intervals) of rheumatoid arthritis in five central hospital districts in the central part of the study area included in our previous study in 1980, 1985, 1990, and 1995. The figures are age adjusted to the Finnish adult population in 1990
| Area | 1980 | 1985 | 1990 | 1995 | p Value3-150 |
| Kotka | 38.6 (29.6 to 50.0) | 34.6 (26.0 to 45.1) | 24.4 (17.5 to 33.9) | 31.1 (23.1 to 41.5) | 0.113 |
| Lahti | 30.5 (22.5 to 40.4) | 34.0 (25.5 to 44.1) | 32.4 (24.1 to 42.1) | 27.9 (20.6 to 37.3) | 0.637 |
| Tampere | 44.8 (38.0 to 52.8) | 41.3 (34.8 to 48.9) | 30.3 (24.9 to 36.8) | 26.6 (21.5 to 32.5) | <0.001 |
| Jyväskylä | 48.6 (39.0 to 59.4) | 44.2 (35.6 to 54.8) | 41.4 (32.7 to 51.1) | 43.1 (34.4 to 52.9) | 0.361 |
| Kuopio | 33.5 (25.9 to 42.6) | 38.8 (30.8 to 48.6) | 31.1 (23.9 to 39.7) | 36.3 (28.7 to 45.7) | 0.958 |
↵3-150 Mantel-Haenszel test for linear association.