Long-Term Outcomes in Juvenile Idiopathic Arthritis: Eighteen Years of Follow-Up in the Population-Based Nordic Juvenile Idiopathic Arthritis Cohort.

Objective: The present study was undertaken to assess the long-term course, remission rate, and disease burden in juvenile idiopathic arthritis (JIA) 18 years after disease onset in a population-based setting from the early biologic era.

Methods: A total of 510 consecutive cases of JIA with disease onset between 1997 and 2000 from defined geographic regions in Denmark, Norway, Sweden, and Finland were prospectively included in this 18-year cohort study. At the follow-up visit, patient-reported demographic and clinical data were collected.

Results: The study included 434 (85%) of the 510 eligible JIA participants. The mean ± SD age was 24.0 ± 4.4 years. The median juvenile arthritis disease activity score in 71 joints (JADAS-71) was 1.5 (interquartile range [IQR] 0-5), with the enthesitis-related arthritis (ERA) category of JIA having the highest median score (4.5 [IQR 1.5-8.5], P = 0.003). In this cohort, 46% of patients still had active disease, and 66 (15%) were treated with synthetic disease-modifying antirheumatic drugs and 84 (19%) with biologics. Inactive disease indicated by a JADAS-71 score of <1 was seen in 48% of participants. Clinical remission off medication (CR) was documented in 33% of the participants with high variability among the JIA categories. CR was most often seen in persistent oligoarticular and systemic arthritis and least often in ERA (P < 0.001).

Conclusion: A substantial proportion of the JIA cohort did not achieve CR despite new treatment options during the study period. The ERA category showed the worst outcomes, and in general there is still a high burden of disease in adulthood for JIA.