An analysis published in the December 1999 issue of Diabetologia showed a 3 percent yearly increase in the incidence of type 1 diabetes since 1960.
Based on 37 studies conducted in 27 different countries, this study confirms what many have already concluded and hints at future type 1 rates as high as 50 per 100,000 people in some countries. Recent studies of randomly sampled counties have showed the United States rate to range between 7.8 and 12.3 per 100,000 people.
What Causes This Rise?
Researchers across the world have been investigating possible causes of this global increase of type 1, particularly in children. The December 1999 issue of Diabetic Medicine reported that health authorities in England have set a Diabetes Register in response to a significant increase in the incidence of childhood type 1 in the Cornwall and Devon regions over the past two decades. The increase is especially high in the under-5 age group. Possible reasons include viral infections, infant feeding, cow’s milk and a gene pool that is particularly susceptible to the disease. Globally, the United Kingdom is in the middle to upper ranks of risk.
Islet Antibodies in Cord Blood Could be a Clue
Another study appearing in the December 1999 Diabetologia found that the mothers of 14 out of 81 type 1 children who had islet antibodies in their cord blood also tested positive for the same autoantibodies. Compared with a control group, the children who eventually developed type 1 diabetes had a much higher prevalence of islet autoantibodies in their cord blood.
Ongoing genetic testing at the Barbara Davis Center for Childhood Diabetes of the cord blood of 20,000 local newborns so far has found that 2.4 percent of them carry the highest-risk genes for diabetes.
The March issue of Diabetes Care reports that a research team from the University of Tampere in Finland is suggesting that the declining frequency of enterovirus infections, which produce mild, flu-like symptoms in the respiratory tract, may explain why the incidence of type 1 diabetes is on the rise globally.
Incidence Skyrocketing in Finland
In Finland, the incidence is now twice as high as it was 30 years ago. Scientists have long fingered enterovirus infections as a culprit for triggering the betacell damage that results in type 1. When a pregnant woman or new mother is exposed to an enterovirus virus, she develops protective antibodies that are passed on to her fetus or newborn. Therefore, the theory goes, if she has not been exposed, her children are more likely to run the risk of developing complications from enterovirus infections such as meningitis and betacell damage.
Steps are also being taken to improve the quality of diabetes screening. Researchers at Sophia Children’s Hospital and Rotterdam Erasmus University use a blood test which looks for islet antibodies in combination with a DNA test to predict with more than 50 percent accuracy whether or not a child will develop type 1 diabetes. By itself, the DNA test would have only 1 percent of accuracy. The islet antibodies test looks for islet antibodies against GAD and IA2, the presence of which are evident of autoimmune islet cell destruction. The symptoms of type 1 diabetes only show up after more than 80 percent of islet cells have already been destroyed.
Similarly, a new method discovered by scientists at the University of Colorado Health Services detailed in the February Proceedings of the National Academy of Science will test for insulin autoantibodies (IAA) in children. Previously, such tests were complicated and required a lot of blood. Four of five children-out of a study population of 934-who consistently tested positive for insulin autoantibodies before they were a year old developed type 1 within three years. Of the remaining 929 children who did not have insulin autoantibodies before age one, only one has developed diabetes. This child, however, tested positive for insulin autoantibodies shortly after his first birthday.