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  What is Type 1 Diabetes?

By Amy Adams, MS

Reviewed By Jeremy Walston, MD and Kristi Silver, MD

Type 1 diabetes affects 700,000 people in the United States and is the most common chronic metabolic disorder to affect children. It is most common in Caucasian populations, especially those in Scandinavia, and rare in people of Asian or African descent. Type 1 diabetes is less common than Type 2 diabetes, accounting for only five to ten percent of all cases.


What is Type 1 diabetes?

Type 1 diabetes occurs when cells of the immune system attack particular cells in the pancreas — called beta cells — that produce insulin. Because all of their beta cells are destroyed, Type 1 diabetics are dependent on insulin injections to control their blood sugar levels. The peak time for developing diabetes is during puberty, although it can occur at any age.



Family Medical History

Out of 100 people with Type 1 diabetes, 80 have no family members with the disease. The remaining 20 people have at least one family member with diabetes. Although most people in the population have a 0.4 percent chance of developing Type 1 diabetes, the risk increases to about two percent if your mother has diabetes and six percent if your father or siblings have Type 1 diabetes. If your sibling with diabetes is a fraternal twin your risk increases to 11 percent and it increases to roughly 50 percent if your identical twin has diabetes.

Because Type 1 diabetes can run in families, researchers have looked for genes that increase a person's risk for developing the disease. So far, they have found roughly 20 different areas on chromosomes that may contribute in varying degrees to a person's chances of developing Type 1 diabetes. No one gene, however, determines if Type 1 diabetes will develop or can be used to predict the development of Type 1 diabetes.



Environmental Factors that Increase Risk

Although researchers have found gene mutations that increase the risk of developing Type 1 diabetes, these genes alone do not cause the disease. There must be a combination of genetic risk and environmental factors to trigger diabetes. When scientists look at identical twins — twins who share all of their genes — they find that if one twin has Type 1 diabetes, the other twin has roughly 50 percent chance of developing the disease. This means that half of the twins who are genetically at risk do not develop diabetes. Therefore, there must be other, nongenetic factors that play a role in diabetes onset.

Researchers aren't sure what environmental factors trigger Type 1 diabetes. Some studies have suggested that drinking cow's milk might increase the risk of developing Type 1 diabetes in people with a genetic risk for the disease.

Drinking cow's milk and exposure to some viruses might trigger Type 1 diabetes in susceptible people

However, these studies are not conclusive. Some doctors recommend breast feeding at-risk children and limiting their intake of cow's milk. Certain types of viral infections — particularly coxsackie B, rubella, and mumps — are also associated with developing Type 1 diabetes in some people. Some researchers think that the virus triggers an immune reaction against the islet cells or in rare cases directly infects and kills these cells. ( For addition factors that may increase diabetes risk, see Related News below.)




Because there is little that can be done to prevent the disease, the American Diabetes Association does not recommend screening children for Type 1 diabetes unless:

  • The child has a parent or sibling with Type 1 diabetes,
  • and
  • The child is going to enter a scientific study that requires these results.
If a child meets these criteria, doctors screen for antibodies to insulin or beta cells. The antibodies indicate a very high risk for developing Type 1 diabetes and can be present up to eight years before symptoms develop.


Related News
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Bigger children may be at risk of type 1 diabetes
Cow's milk may raise diabetes risk in some children


LaPorte, R., M., et al., (1999). Prevalence and Incidence of Insulin-Dependent Diabetes. In (Ed. 2nd), Diabetes in America (pp. 37-14). Bethesda, MD: National Diabetes Data Group, NIH.

National Institute of Diabetes and Digestion and Kidney Diseases (1999). Diabetes Statistics. Bethesda, MD: National Institutes of Health. Publication No. 99-3892.

Dorman, J., et al., (1999). Risk Factors for Insulin-Dependent Diabetes. In Diabetes in America (pp. 165-178). Bethesda, MD: National Diabetes Data Group, NIH.

Scott, F. W. (1990). Cow milk and insulin-dependent diabetes mellitus: is there a relationship? Am J Clin Nutr, 51, 489-91.

Wagenknecht, L. E., et al. (1991). Increased incidence of insulin-dependent diabetes mellitus following an epidemic of Coxsackievirus B5. Am J Epidemiol, 133, 1024-31.

Kyvik, K. O., et al. (1995). Concordance rates of insulin dependent diabetes mellitus: a population based study of young Danish twins [see comments]. Bmj, 311, 913-917.


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