Diabetes is very common. Although its frequency varies with ancestry, an average of one of every nine or ten Canadians has diabetes. More than 90% of these people have type 2 diabetes, while less than 10% have type 1 diabetes. There is no question that genetics plays a role in the development of both types of diabetes. However, diabetes is not inherited in the same way that eye colour or skin colour is inherited. Also, the chance of developing diabetes in someone whose parents have diabetes depends on the type of diabetes they have, and whether one or both parents have diabetes. This is discussed separately below for type 1 diabetes and for type 2 diabetes.
Type 1 diabetes is usually caused by an autoimmune disease in which the body’s immune system damages and eventually destroys a person’s ability to make insulin. The chance of developing autoimmune diseases is partially determined by genetics. On average, a child born to a mother who has type 1 diabetes has about a 3% chance of developing type 1 diabetes before age 30. If the father but not the mother has type 1 diabetes, the child has about a 6% chance of developing type 1 diabetes by age 30. By comparison, if neither parent has type 1 diabetes, the chance that the child of that couple will develop type 1 diabetes is about 0.4% or 4 out of a 1000. Therefore although a parent with type 1 diabetes increases the chance that their child will develop type 1 diabetes by adulthood, the actual risk of 3 to 6% is low.
The chance of developing type 2 diabetes in someone with a family history of type 1 diabetes is much higher than the chance of developing type 1 diabetes. Indeed, the chance of developing type 2 diabetes is about the same as it is in the general population. A person whose mother or father has type 2 diabetes has about a 40% chance of developing type 2 diabetes during their lifespan. If both parents have type 2 diabetes, the risk rises to about 80%. The chance of developing type 2 diabetes in someone with no family history of type 2 diabetes is not well studied, but the best estimate is about 20%.
There are two take-away messages.
- Regardless of family history a newborn in Canada has about a 20-30% chance of developing any type of diabetes during their lifetime. Because type 2 diabetes is so common, the vast majority will develop type 2 diabetes, regardless of whether a parent had type 1 diabetes.
- The biggest cause of diabetes remains unknown. Diabetes develops due to a combination of genetic predisposition, family history, and the environment that an individual experiences both while developing in their mother’s womb and as they grow into adulthood.
About the author
Hertzel Gerstein
Hertzel is an endocrinologist and professor at McMaster University who is in high demand as a speaker, advocate, and educator on diabetes-related topics. His research focuses on using large, international randomized trials to identify and test new ways of preventing type 2 diabetes, reducing serious health outcomes like strokes and death, and achieving type 2 diabetes remissions.
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