Type 1 diabetes is diagnosed worldwide, and occurs in every race and nationality. The incidence (or frequency) of the disorder is increasing in every population.
Type 1 diabetes is most common in white people or individuals of Northern European heritage, in whom the incidence is 1 out of every 300 or 400 individuals. Finland and Sardinia are “hot spots” where the risk of type 1 diabetes is 1 out of every 100 to 200 people. The reasons for the geographical and racial differences are not understood.
The presence of antibodies directed against beta cell antigens or molecules is a significant risk factor for the development of type 1 diabetes. The antibodies are directed against proteins associated with the beta cells, such as glutamic acid decarboxylase, tyrosine phosphatase, insulin and heat shock proteins.
Commercial tests are available for:
- glutamic acid decarboxylase (GADAs)
- islet cell antigen 512 (ICA512s or ICA IA-2s)
- insulin auto-antibodies (IAAs)
- islet cell antibodies (ICAs)
- zinc transporter 8 (ZnT8)
Up to 3-5% of the general population may test positive for one of these antibodies, but only about 20% of these individuals will develop diabetes. The presence of two antibodies, however, creates a more than 75% risk of developing type 1 diabetes within the next 10 years.
Among identical twins, it is traditionally reported that only about 40% will both have the disease. Recent research suggests that the number may be much higher. And if one identical twin is positive for antibodies directed against the beta cell, and the other has type 1 diabetes, it is almost certain that both will eventually have diabetes.
A predictive test used in research – the intravenous glucose tolerance test :
Another predictive test, called an intravenous glucose tolerance test (IVGTT), evaluates “first phase” insulin secretion. “First phase” refers to the amount of insulin secreted within the first few minutes after the administration of the intravenous glucose. When someone has a low first phase insulin secretion and two or more antibody tests are positive, there is at least a 90% risk of developing clinical diabetes within the next few years.