Methods. From a prospective population based epidemiological study in southwestern Sweden the cohort of patients with JCA born from 1968 through 1972 were investigated after a median disease duration of 7.1 years. The study cohort constituted of 124 patients with median age 17.7 years.

Results. At followup 49.2% patients still required medication, 20.2% had inactive disease and 30.6% were in remission. The highest risk of continuing disease activity was observed in patients with short disease duration (RR = 9.0) or very long duration (RR = 2.5) compared with those having medium long duration. Girls were 5 times more likely than boys to have continuing disease activity. Based on incidence data from the total population of the epidemiological study it can be estimated that an additional 100 patients with JCA, who were in remission in the beginning of the study, should be included in the present cohort. Thus a total of 60% of the patients with JCA had disease in remission and 70% were rid of disease activity when reaching adulthood in a population based setting.

Conclusion. The selection of patients in studies of the natural history of JCA markedly influences the results, which may be one explanation for the divergent Views of JCA as both a mild and a progressive disease.