LauraM. Jacobsen, MD; Desmond A. Schatz, MD
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.
