Increasing Incidence of Juvenile Idiopathic Arthritis: A Trend Over 31 Years in Southern Sweden

Background The reported incidence of juvenile idiopathic arthritis (JIA) varies from studies around the world, depending on patient collection techniques, geographic region, and time. Our aim was to study the mean annual incidence of juvenile arthritis in a population-based setting using two regional cohorts of children diagnosed with juvenile chronic arthritis (JCA) and JIA over a period of 31 years.Findings The study population was 651 children diagnosed 1980-2010. The mean annual incidence over the period was 9.9 per 100,000 children, with a range from 4.2 per 100,000 in 1980 to 17.1 per 100,000 children in 2010. When comparing incidence rate between the decade of diagnosis using rate ratios, there is a significant difference with diagnosis 1980-1989 as comparator.Conclusions We show a statistically significant increase in the incidence of JIA over three decades in a population-based cohort of children with juvenile arthritis.