FRIDAY, March 22, 2013 — The incidence of type 1 diabetes in children is on the rise worldwide, with the number of new cases growing by an average of 3% per year in youth under age 15. The reasons for the sharp increase remain a medical mystery, since researchers have not been able to identify the changing conditions that are causing more kids to be diagnosed in recent decades. A new study presented this week at the annual Society for Endocrinology conference may help shed more light on this disturbing trend.

“This increase in incidence has been occurring over the last thirty to forty years and genetics don’t change that quickly, so we know this is environment,” said Richard Insel, MD, Chief Scientific Officer for JDRF, an organization that funds type 1 diabetes research. “Something has distinctly changed in the environment.”

Type 1 diabetes is an autoimmune disorder that develops when the body’s immune system mistakenly attacks and destroys the cells in the pancreas that produce insulin. Experts believe the disease is caused by a combination of genetic and environmental factors. Most people that have a genetic predisposition do not develop the disease, but in others, certain environmental factors, still poorly understood, appear to trigger the destructive autoimmune process, eventually leading to type 1 diabetes.

Many Theories, Few Answers

A plethora of factors – everything from new viruses, higher rates of C-section births, pesticides, and gluten consumption – have been offered as possible explanations for the upswing, but some theories are better supported by evidence than others.

The latest study to broach the question, conducted by researchers at the University of Malta, found that countries with lower rates of death from a number of communicable or infectious diseases had a higher incidence of type 1 diabetes. The results provide additional support for the “hygiene hypothesis,” one of the leading theories to explain the increase in type 1 diabetes.

Exposure to an abundant mix of bacteria and viruses at an early age trains the immune system to differentiate between “self cells" and foreign cells. According to the hygiene hypothesis, today's kids may be overprotected from germs because of modern sanitation practices and overuse of antibiotics in medicine and farming. Growing up in a cleaner environment may interfere with normal immune development, potentially leading to autoimmune disorders like type 1 diabetes. On the other hand, in countries where disease-causing microbes are more widespread — as indicated in the study by higher rates of death from infectious disease — children may develop more robust immune systems, possibly explaining the lower rate of type 1 diabetes in those areas.

In other words, the theory is that's it good for kids to play in the dirt, said Marian Rewers, MD, PhD, a pediatric endocrinologist at the University of Colorado School of Medicine. “By eating dirt and getting sick early on, the immune system may be directed in the correct way to fight back, not to react to parts of the body itself,” said Dr. Rewers. “This may be an oversimplified explanation of what might be happening, but it’s plausible.”

While lack of exposure to germs may be contributing to the growing number of kids with type 1 diabetes, there's also evidence that certain viruses may actually cause the disease in people who carry genetic risk factors. The viruses appear to infect the cells in the pancreas that produce insulin, setting off an autoimmune cascade that ultimately progresses to full-fledged diabetes, although the specific strains that cause the disease have not yet been confirmed.

Changes in diet and nutrition have been implicated as well. For example, studies have found that low levels of vitamin D are associated with increased risk of type 1 diabetes. The body can make its own vitamin D from exposure to sunlight, but because parents are using more sunscreen and kids are spending less time outdoors, many young people don't have sufficient levels of the nutrient. However, until controlled trials are performed, it's impossible to know if low vitamin D is actually causing the disease, said Dr. Carol Levy, an endocrinologist at Mount Sinai Hospital.

Other, as yet unidentified factors could also be driving the rise in type 1 diabetes. "The cause may be so simple and close and right in front of our eyes that we are overlooking it,” said Rewers.

“At the end of the day, we’re going to have to get at what’s occurring and why it’s occurring,” said Insel. “There may be multiple things in our environment that have changed. It’s unlikely that just one thing has changed.”

International Study May Reveal Causes

In an effort to pinpoint the environmental triggers that can lead to type 1 diabetes, in 2004, researchers in the U.S. and Europe began a long-term study of nearly 9,000 children who have genes that place them at higher risk for the disease. The TEDDY (The Environmental Determinants of Diabetes in the Young) study is following the children from age 3 months through 15 years to identify those that develop early signs of autoimmune disorder and mature type 1 diabetes and evaluate a number of suspected factors that may contribute to the disease's progression.

To monitor children's exposure to microbes like viruses and bacteria that may play a role, the researchers are collecting blood, stool, and other samples at regular intervals. The investigators are also compiling a wealth of data on other factors that may impact risk, including diet during the first few years of life, duration of breastfeeding, vitamin levels, and stress.

The hope is that by the completion of the study in 2025, scientists will have isolated the causes at the root of the recent type 1 surge. “If we identify these factors we may be able to build a prevention around them,” said Rewers, who serves as co-chair of the TEDDY steering committee. “If it’s a new infection, we can develop a vaccine against it.” If the hygiene hypothesis is supported by the findings, countries may need to reevaluate the widespread use of antibiotics, he said.

According to Rewers, the mystery may be starting to unravel. “We are not able to say the cause of diabetes, but we do have very important clues concerning where we are heading,” said Rewers. “The first papers that review the cause [of type 1 diabetes] may be completed in the next three years.”

Unfortunately, until the causes are known, there are no proven steps individuals can take to prevent the development of type 1 diabetes.

“There are still a lot of questions that we don’t have sorted out at this point,” said Dr. Levy. "The most important thing is to do more research and get answers to these questions so that we can give people good information.”