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A jump in the number of 'lower-risk' children being diagnosed with type 1 diabetes, has contributed to a doubling in the number of cases over the past 20 years, say Australian researchers.
Endocrinologist Dr Spiros Fourlanos from the Royal Melbourne Hospital and his colleagues report their findings in Diabetes Care, which suggests environmental factors, such as sedentary lifestyle, may be the cause.
Previous research has found the incidence of children diagnosed with type 1 diabetes has doubled in Australia over the past two decades.
In previous decades people with intermediate or low risk human leukocyte antigen (HLA) genes were least likely to progress to diabetes in childhood.
But the new study suggests a growing number of children diagnosed with type 1 diabetes have intermediate risk HLA genes.
The study examined 462 Victorians who had been diagnosed with childhood type 1 diabetes since 1950.
Between 1950 and 1969, 79% of children diagnosed with type 1 diabetes high risk HLA genes. In the period 2000 to 2005, this had dropped to 28%. Simultaneously those with intermediate risk HLA genes jumped from 20% to 48%, those with low risk genes remained stable at 3%.
"We found that surprisingly type 1 diabetes was starting to develop more often in the lower risk groups - occurring increasingly in those with intermediate risk genes. Previously this was much less common," co-researcher and Royal Melbourne Hospital director of diabetes and endocrinology, Professor Peter Colman says.
"High risk genes used to account for most cases but now more are lower risk genes."
Researchers believe environmental factors including obesity, reduced exercise or vitamin D deficiency due to reduced sunlight exposure, could be interacting with the HLA genes trigger childhood type 1 diabetes.
Colman says that while the link between childhood obesity and type 2 diabetes is well known, researchers now believe lifestyle factors may also contribute to type 1 diabetes.
He adds that the average age of children diagnosed with type 1 diabetes with either immediate or low risk HLA genes, had decreased from eight and half years old, to six years old.
Colman cautions that "still only a small proportion of those who have the HLA genes will develop type 1 diabetes."
"However disease incidence and the ratio of intermediate to high risk genes is continuing to increase so there is a much larger pool of people with this genetic risk type, meaning a bigger possible pool of people who can potentially develop diabetes," he says.
Colman says 3% of first degree relatives (i.e. sisters and brothers) of those diagnosed with type 1 diabetes will develop the disease. As a result, an increasing number of siblings are being tested, in the hope new future treatments such as intra-nasal and oral insulin, or gene therapy, could prevent its progression.
Copyright Jewish Diabetes Association. Last updated June 2017©