There is a large geographical variation in the incidence of Type 1 diabetes. In Europe, the frequency increases as from South to North although there is considerable variation between countries. The highest incidence of diabetes is seen in colder autumn and winter months and it is slightly more common in males than females (ratio 1.3:1).
The frequency of Type 1 diabetes is increasing by about 3% per year in most areas of the world.
Environmental factors contribute significantly to the risk of developing Type 1 diabetes but the causative or triggering factor is not known. There is also an inherited risk for developing Type 1 diabetes. One in twenty siblings of affected children will also develop the condition in childhood. It appears that in order to develop Type 1 diabetes an environmental trigger is required to activate an inherited tendency.
The cause of Type1 diabetes is linked to auto immunity. The pancreatic islet cells of patients with newly diagnosed Type 1 diabetes contain chronic inflammatory mononuclear cell infiltrate, primarily T lymphocytes and macrophages.
As the disease progresses there is complete loss of the β-cells that secrete insulin. This inflammatory reaction can also be identified in the form of circulating auto antibodies. In newly diagnosed Type 1 diabetic patients, circulating islet cell autoantibodies (ICAs), glutamic acid decarboxylase (GAD) autoantibodies, insulin autoantibodies (IAAs) and IA-2 antibodies can be found.
Islet autoantibodies persist for a period of a few months to a few years before the development of diabetes. However, not all those with antibodies progress to full blown diabetes. Type 1 diabetes is also associated with other organ-specific autoimmune disorders.
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