Extended Family History of Diabetes and Autoimmune Diseases in Children With and Without Type 1 Diabetes

OBJECTIVE To determine the extended family history of diabetes or autoimmune diseases in families with and without children having type 1 diabetes. RESEARCH DESIGN AND METHODS Three hundred case families and 381 control families were interviewed using structured questionnaires. RESULTS The proportion of case children having at least one relative with type 1 diabetes outside the nuclear family was higher than that of control children (50.3 vs. 31.8%, P < 0.001). The proportions of case and control children having relatives with type 2 diabetes or gestational diabetes were similar. Other autoimmune diseases occurred more frequently among the case children (9.7 vs. 1.1%, P < 0.001), in the case nuclear families (22.0 vs. 12.9%, P = 0.002) and in relatives outside the case nuclear family (72.0 vs. 62.2%, P = 0.007). CONCLUSIONS Type 1 diabetes and autoimmune diseases not only cluster in the nuclear families of children with type 1 diabetes but are also overrepresented in their extended families.