Is the epidemiology of rheumatoid arthritis changing? Results from a population-based incidence study, 1985-2014.

Significant increase in incidence of RF-negative RA and decrease in RF-positive RA in 2005-2014 compared with previous decades was found using 1987 ACR criteria. The incidence of RA overall during this period remained similar to the previous decade. The changing prevalence of environmental factors, such as smoking, obesity and others, may have contributed to these trends. Whether these trends represent a changing serological profile of RA requires further investigation.