The age at onset of rheumatoid arthritis is increasing in Japan: a nationwide database study

Aim To determine whether the age at onset of rheumatoid arthritis (RA) has increased in Japan using a nationwide database (National Database of Rheumatic Diseases by iR-net in Japan, NinJa). Method We analyzed the data of RA patients who had been diagnosed with early RA (disease duration < 2 years) and newly registered in 2003, 2008 or 2013. Results The numbers of patients who developed RA in 2002–2003, 2007–2008, and 2012–2013 were 536, 812 and...