DAS28-CRP significantly underestimated disease activity and overestimated the improvement in disease activity compared with DAS28-ESR. DAS28-CRP should be evaluated using different criteria from that for DAS28-ESR.

Patients with RA had no higher overall incidence of malignancies, but lymphoma was significantly more frequent than in the general population.

We have demonstrated that the age at RA onset in Japan has increased significantly over the last decade. This can be attributed to Japan's aging population. In addition, the high prevalence of RA among the first baby boomers suggests that environmental factors might also have contributed to the increase in age at RA onset in Japan.

The overall incidence of orthopedic surgeries in patients with RA significantly decreased, accompanied by improved clinical outcomes because of the expanded use of effective drugs; however, the declining trend differed between procedures or locations. The results from the present study suggest that there might be a change in supply and demand for orthopedic surgeries.