Association and Familial Coaggregation of Type 1 Diabetes and Eating Disorders: A Register-Based Cohort Study in Denmark and Sweden

OBJECTIVE: To ascertain the association and coaggregation of eating disorders and childhood-onset type 1 diabetes in families. RESEARCH DESIGN AND METHODS: Using population samples from national registers in Sweden (n = 2,517,277) and Demark (n = 1,825,920), we investigated the within-individual association between type 1 diabetes and eating disorders and their familial coaggregation among full siblings, half siblings, full cousins, and half cousins. On the basis of clinical diagnoses, we classified eating disorders into any eating disorder (AED), anorexia nervosa (AN) and atypical AN, and other eating disorder (OED). Associations were determined with hazard ratios (HRs) with 95% CIs from Cox regressions. RESULTS: Swedish and Danish individuals with a type 1 diabetes diagnosis had a greater risk of receiving an eating disorder diagnosis (HR [95% CI] Sweden: AED 2.02 [1.80–2.27], AN 1.63 [1.36–1.96], OED 2.34 [2.07–2.63]; Denmark: AED 2.19 [1.84–2.61], AN 1.78 [1.36–2.33], OED 2.65 [2.20–3.21]). We also meta-analyzed the results: AED 2.07 (1.88–2.28), AN 1.68 (1.44–1.95), OED 2.44 (2.17–2.72). There was an increased risk of receiving an eating disorder diagnosis in full siblings in the Swedish cohort (AED 1.25 [1.07–1.46], AN 1.28 [1.04–1.57], OED 1.28 [1.07–1.52]); these results were nonsignificant in the Danish cohort. CONCLUSIONS: Patients with type 1 diabetes are at a higher risk of subsequent eating disorders; however, there is conflicting support for the relationship between having a sibling with type 1 diabetes and an eating disorder diagnosis. Diabetes health care teams should be vigilant about disordered eating behaviors in children and adolescents with type 1 diabetes.