Later Onset Type 1 Diabetes Often Misdiagnosed as Type 2

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Type 1 diabetes used to be commonly known as juvenile diabetes because it was often diagnosed in childhood. In individuals with this disease, the body mistakenly attacks and destroys insulin-producing beta cells, and eventually the body is no longer able to generate enough insulin to support normal blood sugar levels. Therefore, individuals must monitor their own blood-glucose and inject themselves with insulin.

However, research has shown that around 42% of people with type 1 diabetes were diagnosed after age 30. A recent study found that some people are mistakenly diagnosed with type 2 diabetes instead due to the late onset of the disease as well as clinical and genetic characteristics. This can make it difficult to properly differentiate between the two conditions.

The study examined data from 583 participants diagnosed with diabetes after age 30 who are part of the Exeter Diabetes Alliance for Research in England (DARE). Their data was compared to 220 DARE participants with the same study criteria but who were diagnosed with type 1 diabetes before age 30.

The researchers wanted to know how many of those diagnosed after age 30 had severe endogenous insulin deficiency (meaning their body naturally produced little to no insulin on its own), whether diagnosed with type 1 or type 2 diabetes. Severe insulin deficiency is a classic sign of type 1 diabetes but C-peptide and other tests are not always conducted to check for this condition in adults age 30 or older. However, the study found that 21 percent of participants who were treated with insulin had this condition, and 38% of participants not treated with insulin at diagnosis had it.

Individuals who required rapid insulin within one year of diagnosis or who were treated with insulin within three years of diagnosis had a higher likelihood of severe endogenous insulin deficiency; 85% and 47% respectively. This means that they likely had type 1 diabetes rather than type 2, regardless of what their initial diagnosis was. Participants diagnosed after age 30 shared very similar clinical and biological characteristics with the younger cohort.

It is critical that physicians conduct necessary testing to differentiate type 1 from type 2 diabetes regardless of age of onset. There are often different protocols for treating each of these conditions, and individuals with type 1 diagnoses have greater access to necessary resources such as continuous glucose monitoring (CGM) devices, insulin-pump therapy, and targeted diabetes education.

With more awareness of the frequency of type 1 diabetes onset after age 30 and associated characteristics, hopefully medical providers will be better able to assess and accurately diagnose this condition more quickly to provide essential treatment.

The Diabetes Research Connection (DRC) strives to support early career scientists in pursuing novel research studies that focus on the prevention, diagnosis, and treatment of type 1 diabetes as well as improving quality of life for individuals living with this disease. Research is critical to one day finding a cure.

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