MINI-EPIDEMICS of type 1 diabetes appear to be occurring among Australian children every five years, a landmark study that points to an environmental cause of the autoimmune disease shows.
The study found that type 1 diabetes, a condition that occurs when the body's immune system seems to spontaneously attack and kill the cells that produce insulin, has also been inexplicably increasing by more than 2 per cent every year.
The researchers reviewed every new case of type 1 diabetes in Western Australia over 25 years, finding that while the illness was on the rise, it was doing so with an even flow of peaks and troughs.
In some cases there was a difference of up to 20 per cent between the peak and low years, the study, published in the journal Diabetes Care, says.
One of the co-authors, Professor Tim Jones, said that while there must be some reason for both the increase and the cyclical pattern of the condition, it was not yet understood.
"We don't really know what the triggers are. There are probably multiple triggers, including environmental factors such as viruses and toxins," he said. "There have been increases in allergies at the same time [as type 1 diabetes has increased], so it may reflect similar underlying causes."
When his team compared the pattern in West Australia with similar research done overseas, they found it to be "almost identical" to a pattern found in northern England, despite the two areas having very different demographic and climatic conditions. The data suggests another peak beginning this year, with previous ones occurring in 2007 and 2002.
More than 87,000 Australians have been diagnosed with type 1 diabetes, the most recent figures from the Australian Institute of Health and Welfare show.
Professor Jones said the peaks could be caused by cycles in which viruses are dominant, similar to those with cold and flu viruses, where different strains are common each year.
He said research was now being done to monitor babies who could be at risk of the condition because their parents have it, to try to track what made them develop it.
However, it is complicated by the fact that about 80 per cent of children whose parents have type 1 diabetes will not develop the condition.
The national policy adviser for Diabetes Australia, Greg Johnson, said people often mistakenly believed that type 1 diabetes was an inherited condition. "There is not a common understanding that there are clearly environmental factors at play," he said.
But he cautioned that further studies would be needed before it was clear that viruses were the cause.
"It's complex. Viruses could be implicated but there might be factors such as chemicals and environmental pollutants or who knows what else," he said.