Epidemiology of juvenile chronic arthritis in southwestern Sweden: a 5-year prospective population study.

Previous epidemiological studies of juvenile chronic arthritis (JCA) report divergent results owing to differences in diagnostic criteria, patient retrieval, and study designs. To investigate incidence and prevalence of JCA in a total population, this prospective survey was performed in southwestern Sweden between 1984 and 1988. Cases were identified using the European League Against Rheumatism criteria for JCA and were reported annually from eight pediatric departments and local pediatricians in the studied area. During the 5 years, 213 new cases of JCA were found, corresponding to an incidence of 54.6 per 100,000 children younger than 16 years of age. The average annual incidence was 10.9 per 100,000. The peak incidence rate, 18.3 per 100,000 was found in girls 0 through 3 years old. The lowest incidence rate, 6.4 per 100,000, was found among boys 12 through 15 years old. In December 1988, 334 cases of JCA were recorded, giving a prevalence of 86.3 per 100,000. When patients in remission were omitted the prevalence was 64.1 per 100,000. The monoarticular+pauciarticular onset type constituted 68.3% of the prevalence cases, while 21.9 were polyarticular and 6.6% had systemic onset. To avoid underestimation of incidence and prevalence, and to get a correct picture of disease patterns, epidemiological surveys of JCA should be population-based rather than referral center-based. Further descriptive studies of JCA in different well-defined geographic areas are important to make valid comparisons. Such comparisons could give clues to etiological factors, both genetic and environmental.