Many obese children and adolescents have impaired glucose tolerance, a condition that often appears before the development of type 2 diabetes, according to researchers funded by the National Institutes of Health (NIH). The study findings appear in the March 14 issue of The New England Journal of Medicine.
"This study suggests that many obese children have a high risk for developing type 2 diabetes," said HHS Secretary Tommy G. Thompson. "Researchers have a lot of information on how to prevent and treat type 2 diabetes in adults, but we need to find better ways to prevent and treat the disease in children."
Once seen only in adults, type 2 diabetes has been rising steadily in children, especially minority adolescents-African Americans, Hispanic Americans, and Native Americans, according to reports from clinics around the country. Although there are no national, population-based data, studies in Cincinatti, Charleston, Los Angeles, San Antonio, and other cities indicate that the percentage of children with newly diagnosed diabetes who are classified as having type 2 diabetes has risen from less than 5 percent before 1994 to 30-50 percent in subsequent years.
"These results strongly imply that intensive efforts to reduce obesity in children and youth who have impaired glucose tolerance will help to prevent their developing type 2 diabetes," said Duane Alexander, M.D., Director of the National Institute of Child Health and Human Development (NICHD). Both NICHD and the National Center for Research Resources (NCRR), another NIH component, funded the study. Both agencies are part of the National Institutes of Health, the HHS agency that sponsors research to uncover knowledge that will lead to better health for everyone.
The scientists from Yale University School of Medicine conducted their study to determine if obese children and teens have impaired glucose tolerance, which, in adults is a known risk factor for type 2 diabetes. The researchers found that the children with impaired glucose tolerance frequently had insulin resistance, a condition that usually precedes type 2 diabetes in adults and is characterized by the inability of fat, muscle, and liver cells to use insulin properly. Eventually, the insulin-producing cells of the pancreas cannot keep up with the body's increasing demand for insulin, glucose builds up in the blood, and type 2 diabetes begins.
"The epidemic of childhood obesity in the United States has been accompanied by a marked increase in the frequency of type 2 diabetes," the study authors wrote.
The researchers tested for impaired glucose tolerance in 55 obese children from 4 to 10 years of age, and 112 obese adolescents from 11 to 18 years of age. In all, 25 percent of the children and 21 percent of the adolescents had impaired glucose tolerance. The researchers also found that four of the adolescents in the study had silent type 2 diabetes, a form of diabetes that doesn't cause any symptoms.
"Impaired glucose tolerance is highly prevalent among children and adolescents with severe obesity, irrespective of ethnic group," the researchers wrote.
The National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), the part of the NIH with lead responsibility for diabetes research, is funding clinical trials to prevent and treat type 2 diabetes in children. These studies, currently being planned for recruitment next year, will try to develop ways to stem the rising rate of type 2 diabetes in children and to treat the disease safely and effectively in those who do develop it.
The prevention trials will focus on developing cost-effective interventions that can be widely applied in schools and communities across the country. "For children who already have type 2 diabetes, it's critical to give the safest, most effective therapy as early as possible, yet we can't assume that the therapies used in adults have the same safety and efficacy profiles for children," said study chair Dr. Francine Kaufman, president elect of the American Diabetes Association and director of the Comprehensive Diabetes Center at the Children's Hospital of Los Angeles. Many drugs are available to treat type 2 diabetes, but only metformin has been explicitly approved by the Food and Drug Administration for the treatment of type 2 diabetes in children.
The longer a person has diabetes, the greater the chances of developing the disabling, life-threatening complications of diabetes. "We are seeing young people in their late teens who are already developing the complications of type 2 diabetes," said Dr. Kaufman.
Type 2 diabetes in children, as in adults, is closely linked to obesity, a sedentary lifestyle, and a family history of diabetes. The prevalence of obesity has nearly tripled in adolescents in the past 20 years. According to The Surgeon General's Call to Action to Prevent and Decrease Overweight and Obesity, 13 percent of children 6 to 11 years old and 14 percent of adolescents 12 to 19 years old in the United States were overweight in 1999. Overweight children are at increased risk of developing type 2 diabetes during childhood and later in life. Genetic susceptibility as well as lack of physical activity and unhealthy eating patterns all play important roles in determining a child's weight. They also contribute to a child's risk for type 2 diabetes and other complications of overweight. About 16 million people in the United States have diabetes. It is the main cause of kidney failure, limb amputations, and new onset blindness in adults and a major cause of heart disease and stroke. Type 2 diabetes accounts for up to 95 percent of all diabetes cases. Most common in adults over age 40, this form of diabetes affects 8 percent of the U.S. population age 20 and older. The prevalence of type 2 diabetes has tripled in the last 30 years, due in large part to the upsurge in obesity. People who are obese, defined as a body mass index (BMI) of 30 or greater have a five-fold greater risk of diabetes than those with a normal BMI of 25 or less.
Type 1 diabetes affects about 1 million people in the United States. This form of diabetes develops when the body's immune system destroys pancreatic beta cells, the only cells in the body that make the hormone insulin, which regulates blood glucose. Type 1 diabetes usually strikes children and young adults, who need several insulin injections a day or an insulin pump to survive. Insulin is the only treatment for type 1 diabetes, but it is not a cure, nor can it reliably prevent the long-term complications of the disease.
The National Center for Research Resources (NCRR) supported this research through grants to Yale University for two General Clinical Research Centers that host adult and child studies. NCRR funding provides NIH-supported investigators with access to specialized basic and clinical research facilities, technologies, instrumentation, biomaterials, animal models, genetic stocks, and more.