Type 1 diabetes delayed when parents have type 2

Among people who develop type 1 diabetes, the age it starts tends to be later if their parents have type 2 diabetes, Finnish researchers have found.

Type 1 diabetes is an autoimmune condition in which the body mistakenly attacks insulin-producing cells, and it usually starts in childhood; type 2 diabetes is a metabolic derangement, often tied to obesity later in life.

Few studies have looked at how a family history of type 2 diabetes impacts the offspring with type 1 disease, according to a report in the medical journal Diabetes Care.

To investigate, Dr. Per-Henrik Groop, from Helsinki University Hospital, and colleagues analyzed data from 1860 patients with type 1 diabetes. About a third of the subjects had parents with type 2 diabetes.

On average, the onset of type 1 diabetes occurred at 17.2 years of age in the group with a family history compared with 16.1 years in the group without parental diabetes.

There doesn't seem to be a clear explanation for this finding, which is unexpected since an inherited risk for diabetes might tend to accelerate rather than retard the onset of type 1 diabetes. The researchers say the possibility that the type 1 diabetics might have actually included some with type 2 diabetes "does not seem to be the answer."

By Anthony J. Brown, MD
SOURCE: Diabetes Care, January 2009.