Health, can you please provide the source of your statement? The following is from the JDRF website. Please note the second paragraph where it states that only 5% people are at risk if a parent, sibling, or child has the disease.
Is type 1 diabetes hereditary?
Researchers are still trying to get a clear picture about how genes and environmental factors interact to determine a person’s risk of developing type 1 diabetes. Forty percent of everyone in the United States carries one or more of the HLA genes (human leukocyte antigen) which lead to increased risk of type 1 diabetes. To be at increased risk, however, an individual needs two copies of these genes, one from each parent.
One in 400-500 people in the general population develops type 1 diabetes, but 1 in 20 (5 percent) people are at risk if a parent, sibling, or child has the disease. Research has shown, however, that genes don’t tell the whole story, and suggests that environmental factors (which are not yet fully known) play a role as well.
JDRF is currently funding a study that will follow more than 7,000 newborns at increased genetic risk of developing diabetes and will collect vast amounts of data on potential environmental factors over a 15-year period to see which ones are associated with a greater or lesser risk of developing diabetes