What are the risk factors for type one and two 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

Read more in the Diabetes: Facts and Stats, Diabetes UK.

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 one in two, or 50% chance, of inheriting the affected gene.