Australian researchers say that environmental factors like sedentary lifestyle may be to blame for a rise in the number of cases of childhood type 1 diabetes.
Endocrinologist Dr Spiros Fourlanos from the Royal Melbourne Hospital says that studies have shown that the incidence of children diagnosed with type 1 diabetes has doubled in the country over the past two decades.
He says that people with intermediate or low risk human leukocyte antigen (HLA) genes had a very low likelihood of progressing to diabetes in childhood in previous decades.
However, adds the researcher, his latest study shows that a growing number of children diagnosed with type 1 diabetes have intermediate risk HLA genes.
During the study, Dr. Fourlanos and his colleagues examined 462 Victorians who had been diagnosed with childhood type 1 diabetes since 1950.
While 79 per cent of the children diagnosed with type 1 diabetes high risk HLA genes between 1950 and 1969, the number had dropped to 28 per cent from 2000 to 2005.
Simultaneously, subjects with intermediate risk HLA genes jumped from 20 per cent to 48 per cent, and those with low risk genes remained stable at three per cent.
"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," ABC Online quoted co-researcher and Royal Melbourne Hospital director of diabetes and endocrinology, Professor Peter Colman, as saying.
"High risk genes used to account for most cases but now more are lower risk genes," he added.
The researchers said that perhaps environmental factors-like obesity, reduced exercise or vitamin D deficiency due to reduced sunlight exposure-interact with the HLA genes to trigger childhood type 1 diabetes.
Colman said that scientists had started to believe that lifestyle factor might play a significant role in the development of type 1 diabetes.
He said 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.
"Still only a small proportion of those who have the HLA genes will develop type 1 diabetes," said Colman.
"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 added.
The researcher said that three per cent of first degree relatives (i.e. sisters and brothers) of the people diagnosed with type 1 diabetes would develop the disease.
Consequently, an increasing number of siblings were being tested, in the hope new future treatments like intra-nasal and oral insulin, or gene therapy, could prevent its progression.