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How does a family history affect my risk of diabetes?

Genetic risk in type 1 diabetes

According to Diabetes UK:

‘Although more than 85% of type 1 diabetes occurs in individuals with no previous first degree family history, the risk among first degree relatives is about 15 times higher than in the general population.

On average:

  • if a mother has Type 1 diabetes, the child’s risk of developing it is about 2–4 per cent
  • if a father has the condition, the child’s risk of developing it is about 6–9 per cent
  • if both parents have the condition, the child’s risk of developing it is up to 30 per cent
  • if a brother or sister develops the condition, the sibling’s risk of developing it is 10 per cent (rising to 10–19 per cent for a non-identical twin and 30–70 per cent for an identical twin).’

These observations point to a multifactorial aetiology with both environmental and genetic contributions. Suggested environmental factors include diet, viral exposure in early childhood, and certain drugs. The disease process involves irreversible destruction of insulin-producing islet beta cells in the pancreas by the body’s own immune system, perhaps as a result of an interaction between infection and an abnormal genetically programmed immune response.

Genetic risk in type 2 diabetes

According to Diabetes UK:

There is a complex interplay of genetic and environmental factors in type 2 diabetes. It tends to cluster in families. People with diabetes in the family are 2-6 times more likely to have diabetes than people without diabetes in the family.

  • If you have a parent with type 2 diabetes you have a 30% lifetime risk of developing type 2 diabetes
  • If both your parents have type 2 diabetes you have an 80% lifetime risk of developing type 2 diabetes

You can read more in the Diabetes: Facts and Stats, Diabetes UK.

We will learn more about the genetic causes of multifactorial diabetes (Type 1 and Type 2) in Week 2.

Genetic risk in Monogenic diabetes

The commonest types of monogenic diabetes are characterised by autosomal dominant inheritance with each child of an affected parent having a 1 in 2, or 50% chance of inheriting the affected gene. You’ll find more examples of inheritance in monogenic diabetes next week.

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This article is from the free online course:

Genomic Medicine: Transforming Patient Care in Diabetes

University of Exeter