Epidemiology and comorbidity of juvenile idiopathic arthritis in Poland- a nationwide study

Background Diagnostic pathways for patients with juvenile idiopathic arthritis (JIA) have gradually improved over time. Provider practice has also shifted towards goal-oriented treatment with disease-modifying drugs (DMARDs) that together may have changed the epidemiologic landscape of JIA. Methods Public healthcare utilization records from the National Health Fund (NHF) were screened between 2010 and 2022. For individuals aged < 16 years, we utilized a narrow JIA case definition combining repeat ICD-10 encoding with DMARDs prescription based on ATC codes. Results In 2022, we identified 1,625 incident and 29,758 prevalent JIA cases (< 16 years), which corresponds to incidence (IRs) and prevalence rates of 4.30 and 78.80 per 100,000 persons of the general population. For the pediatric population, annual IRs for JIA (< 16 years) ranged between 24.0 (95% CI 22.8, 25.2) and 38.7 (95% CI 37.2-40.3) per 100,000. Greater susceptibility among females was also consistently observed with the annual IR ratio ranging between 1.16 and 1.53. The most common concurrent disorders based on medical care services were allergic rhinitis (N = 5,200, 17.5%), bronchial asthma (N = 3,661, 12.3%) and chronic tonsillitis/pharyngitis (N = 3641, 12.2%). Analysis of 214,285 outpatient care visits revealed a median (IQR, range) annual healthcare cost of 37.8<euro> (35.8-47.4<euro>, 30.3-86.1<euro>) per JIA patient. Conclusions This comprehensive, nationwide study provides a contemporary estimate of JIA burden in Poland. Our findings indicate that both the occurrence of new cases and overall burden of JIA in the past ten years align with the lower end of projected figures for our geographical area, especially when compared with Scandinavian nations. Key messages center dot In comparison to higher welfare nations, comprehensive data on JIA epidemiology from lower income countries in Europe are scarce. center dot This nationwide, healthcare system analysis examines temporal changes in JIA burden of the Polish population, including co-morbidities and direct costs of ambulatory care. center dot Cyclic and age-dependent trends in incidence rates were observed, with significant comorbidity recorded for every fourth patient with JIA.