Objective. It is often difficult to determine the pathophysiology of childhood diabetes at onset, particularly in overweight children, because obesity has been associated with both type 1 and type 2 diabetes. We compared children at the diagnosis of diabetes in a multiethnic population-based registry to understand the epidemiology of the disease during a time of rapidly changing diagnostic and treatment norms.

Methods. Incident diabetes was ascertained in Chicagoans who were aged 0 to 17 years from 1985 to 2001. We classified as type 2 those with polycystic ovary syndrome, acanthosis, or a physician's note indicating type 2 or those who reported subsequent use of oral agents (n = 203); 73% of them were also obese. Patients with obesity at onset but no other indicator of possible type 2 (n = 197) were classified as having obesity-related/undetermined type. The remaining 842 cases were classified as type 1. Logistic regression analyses were conducted.

Results. Fully 32% of cases were classified as non–type 1, including 37% of non-Hispanic blacks, 30% of Latinos, and 14% of non-Hispanic whites. The proportion of obesity-undetermined and type 2 increased over the 17 years. Comparing the 3 patient groups, type 2 cases were more often female, non-Hispanic black, and older and had a first-degree diabetic relative, whereas Latino boys were overrepresented among the obese/undetermined.

Conclusion. Obesity is prevalent in youths with newly diagnosed diabetes, particularly during recent years. The growth in non–type 1 diabetes in children since 1985 likely reflects both a true increase and greater physician awareness of the possibility that type 2 diabetes may occur in children.

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