Comorbidity of type 1 diabetes and juvenile idiopathic arthritis.

OBJECTIVE To analyze the prevalence of juvenile idiopathic arthritis (JIA) and diabetes end points in pediatric patients with type 1 diabetes. STUDY DESIGN Patients with type 1 diabetes, recorded from 1995 up to September 2013 in the Diabetes Patienten Verlaufsdokumentation database (n = 54,911, <16 years of age, 47% girls), were analyzed. The patients' height, weight, and body mass index SDS, glycosylated hemoglobin A1c (HbA1c); insulin dose; hypertension and dyslipidemia prevalence; rate of hypoglycemic events; and ketoacidosis were compared between patients with and without JIA. To adjust for age, sex, diabetes duration, and migration background, data were analyzed in hierarchic multivariable regression models. RESULTS The prevalence of JIA in type 1 diabetes was 106 of 54,911 patients; 66% were girls. Diabetes onset was earlier in children with JIA (7.2 years vs 8.3 years, P = .04). Children with JIA were smaller (SDS: -0.22 vs 0.09, P = .004). Correspondingly, weight SDS was lower in patients with JIA (-0.02 vs 0.22, P = .01). Body mass index SDS did not differ. HbA1c was marginally lower in children with JIA (63 mmol/mol [8.0%] vs 67 mmol/mol [8.3%], P = .06). Insulin requirement was greater in patients with JIA (1.03 vs 0.93 insulin units/weight/day, P = .003). Hypertension and dyslipidemia were comparable in both groups. CONCLUSIONS The JIA-prevalence in patients with type 1 diabetes (0.19%) was considerably greater than in the general population (0.05%). Growth is influenced negatively by JIA. Surprisingly, HbA1c was somewhat lower in children with JIA, possibly because of a more intensive treatment or a latent hemolysis caused by the inflammation.