Type 1 Diabetes

Importance: Type 1 diabetes is defined by hyperglycemia due to autoimmune destruction of the insulin-producing beta cells in the pancreas, leading to insulin deficiency, and accounts for 5% to 10% of all cases of diabetes. Type 1 diabetes affects approximately 2 million people in the US and 8.4 million people worldwide and is associated with microvascular and macrovascular complications such as retinopathy, nephropathy, neuropathy, and cardiovascular disease. Observations: Ninety percent to 95% of people with type 1 diabetes have at least 1 autoantibody when they are diagnosed with diabetes. These autoantibodies include autoantibodies to insulin, glutamic acid decarboxylase 65, insulinoma-associated 2, and zinc transporter 8 autoantibodies and are absent in type 2 diabetes or monogenic diabetes (a rarer form of diabetes caused by a single genetic variant). These autoantibodies are present before clinical symptoms develop and can identify early stages of type 1 diabetes. Up to 44% of children and 23% of adults with type 1 diabetes present with diabetes-related ketoacidosis. Type 1 diabetes is most commonly diagnosed between ages 10 and 14 years, but the median age of diagnosis in the US is 24 years. People with type 1 diabetes require lifelong insulin replacement, which can be administered via subcutaneous injection or insulin pump. Insulin regimens that mimic normal physiology include long-acting basal insulin (eg, glargine or degludec) administered once to twice daily and rapid-acting bolus insulin (eg, aspart or lispro) administered prior to meals that contain carbohydrates and during periods of hyperglycemia. Randomized clinical trials have demonstrated that continuous glucose monitors with insulin pumps, which automatically adjust insulin delivery in response to glucose levels, result in less hypoglycemia and improved hemoglobin A1c levels (with the greatest improvement occurring in those with higher starting levels [eg, >8.0%]). Conclusions and Relevance: Type 1 diabetes accounts for 5% to 10% of all cases of diabetes and is characterized by the presence of islet autoantibodies in 90% to 95% of patients. Lifelong use of insulin therapy is currently required for treatment of type 1 diabetes.