Juvenile Idiopathic Arthritis in Olmsted County, Minnesota, 1960-2013.

OBJECTIVE: To evaluate the incidence and prevalence of juvenile idiopathic arthritis (JIA) in Olmsted County, Minnesota in 1994-2013 and trends in juvenile rheumatoid arthritis (JRA) in 1960-2013.

METHODS: Cases of arthritis in 1994-2013 were identified by diagnosis code with medical chart review to confirm diagnosis separately for JIA and JRA. Overall incidence rates with 95% confidence intervals (95% CIs) were age and sex adjusted to the 2010 US white population. Comparisons were made with an earlier (1960-1993) cohort from this same population.

RESULTS: Seventy-one incident cases of JIA in 1994-2013 were identified, with an overall age- and sex-adjusted incidence rate of 10.3 per 100,000 (95% CI 7.9-12.7). Forty-two (59%) were female, with an incidence of 12.4 per 100,000 (95% CI 8.6-16.2), as compared to 8.3 per 100,000 (95% CI 5.2-11.3) in males. The most common subtype was oligoarthritis (63%). The mean ± SD age at diagnosis was 8.2 ± 5.3 years. The prevalence of JIA on January 1, 2000 and January 1, 2010 was 51.0 per 100,000 (95% CI 25.2-76.8) and 57.6 per 100,000 (95% CI 31.0-94.5), respectively. When the annual incidence of JRA was compared over time from 1960 to 2013, there was no significant change in incidence overall; however, the incidence decreased among females (P = 0.003). A cyclic pattern of incidence was observed, with peaks approximately every 10 years. Similar to the findings with regard to incidence, prevalence did not change overall, but decreased among females (P = 0.048). There were 4 deaths in the cohort of JRA patients diagnosed in 1960-2013; the standardized mortality ratio was 1.50 (95% CI 0.41-3.83).

CONCLUSION: Incidence of juvenile arthritis overall in Olmsted County, Minnesota has not changed significantly in the past 53 years. A consistent cyclic pattern was noted.