Research by the University of Exeter Medical School using UK Biobank found that adults are as likely to develop type 1 diabetes as children, with more than 40 per cent of type 1 diabetes cases occurring after the age of 30.
But many of those with type 1 diabetes after the age of 30 are thought to have type 2 diabetes at first, and not initially treated with insulin to control blood sugar levels. Previous published research by the University of Exeter Medical School found that, on average, it took a year for those with type 1 diabetes who had been misdiagnosed with type 2 to be put on insulin.
Among the adults with type 1 diabetes to have been misdiagnosed is Theresa May, the Prime Minister, who was initially told by doctors she had type 2 diabetes and given tablets which did not control her blood sugar.
Distinguishing between type 1 or type 2 diabetes matters as it affects the treatment needed. In type 1 diabetes immune cells destroy the body’s insulin producing beta cells and people need to be injected insulin to control blood sugar levels. With Type 2 diabetes there is still insulin produced so it can be treated initially with diet and tablet therapy.
Type 1 diabetes has been typically viewed as a disease of childhood and adolescence as it accounts for more than 85 per cent of diabetes in under 20s.
But type 1 cases are harder to recognise and correctly diagnose in adults because far more people develop type 2 diabetes in later life. Type 2 accounts for 96% of diabetes cases between the ages of 31 and 60, the research shows.
A crucial clue to the possibility of adult–onset type 1 diabetes is the failure of tablets to control blood glucose. Adult-onset type 1 patients are also likely to be slim compared to type 2 patients who are often obese.
Exeter University’s diabetes research team concluded that, although much less common than type 2 diabetes in adulthood, it is crucial that type 1 is diagnosed and treated correctly as it can be life threatening. They found that one in nine of the adult onset type 1 diabetes were admitted to hospital with diabetic ketoacidosis, a potentially fatal condition that develops when type 1 patients are not given insulin.
The study, Frequency and Phenotype of type 1 diabetes in the first six decades of life: a cross-sectional, genetically stratified survival analysis from UK Biobank, published in the Lancet Diabetes & Endocrinology, is the first study to use a novel genetic analysis to identify type 1 diabetes in adults. This allows them to identify cases of type 1 diabetes not picked up by the patients’ doctors.
Dr Richard Oram, a senior lecturer at the University of Exeter and Consultant Physician, said:
“Diabetes textbooks for doctors say that type 1 diabetes is a childhood illness. But our study shows that it is prevalent throughout life. The assumption among many doctors is that adults presenting with the symptoms of diabetes will have type 2 but this misconception can lead to misdiagnosis with potentially serious consequences. The Prime Minister is an example of someone who was misdiagnosed in this way at first. This study should raise awareness that type 1 diabetes occurs throughout adulthood and should be considered as a diagnosis.“
Professor Andrew Hattersley, Professor of Molecular Medicine at the University of Exeter and Consultant Diabetologist at the Royal Devon and Exeter NHS Foundation Trust, said: “The diagnosis of type 1 diabetes in middle and old age is very difficult because almost all patients with diabetes at this age have type 2. Failure to recognise that the diabetes is type 1 rather than type 2 and give appropriate insulin treatment can be dangerous. Type 1 diabetes should be considered for any patient who is rapidly failing to respond to increasing doses of tablets especially if they are slim.”
The study was funded by the Wellcome Trust and Diabetes UK.
Dr Emily Burns, Head of Research Communications at Diabetes UK said: “Type 1 diabetes is much more common than type 2 diabetes in children and young adults. With increasing age, type 2 diabetes becomes more common, making type 1 diabetes less easy to identify. While more research is needed to understand the realities of misdiagnosis, we’d ask healthcare professionals to have this insight in mind: don’t rule out type 1 diabetes after the age of 30.”
To improve knowledge about correctly diagnosing diabetes the Exeter team are at present performing the StartRIGHT study which is funded by NIHR and Diabetes UK. Anyone over 18 who is diagnosed with diabetes in the last year and is now on insulin can sign up. If you’re interested in taking part in the study, please contact the Exeter Clinical Research Facility by emailing firstname.lastname@example.org or calling 01392 408182.
About the StartRIGHT study
The Exeter team is now recruiting people who were diagnosed with diabetes in the last year, to improve diagnosis. They are working on “clinical calculators” – simple websites or smartphone apps which aim to predict the most accurate diagnosis. Funded by Diabetes UK and NIHR, the StartRIGHT study will follow participants for three years following their diagnosis, to see whether the calculator has correctly predicted the type of Diabetes they have. Anyone aged 18 or over and diagnosed with diabetes in the last year who is now on insulin can sign up.