Researchers at Express Scripts Inc. says they believe they are seeing the first concrete signs that obesity is increasing the percentage of U.S. children who have obesity-related diabetes.

The researchers at Express Scripts, St. Louis, a large pharmacy benefits manager, have analyzed Type 1 and Type 2 diabetes medication prescription patterns over a 4-year period for at least 3.7 million U.S. children ages 5 to 19 enrolled in commercial health plans.

Doctors believe that Type 1 diabetes, which destroys the ability of the body to produce insulin, is usually caused by genetic traits, infectious diseases and other factors that trick the body’s immune system into killing insulin-producing tissues.

Doctors believe that Type 2 diabetes, which reduces the ability of the body to handle insulin efficiently, may be caused by obesity and the kinds of diets that lead to obesity.

The Express Script researchers who conducted the newly released study did not try to correlate obesity data with diabetes prescription use, and changes in diabetes awareness and diabetes treatment philosophies may be partly responsible for changes in prescription patterns.

But the researchers at Express Scripts say they did find a dramatic changes in pediatric diabetes prescription patterns between 2002 and 2005.

In the 10-14 age group, for example, the prevalence of use of Type 1 diabetes medications increased 29% over the 4-year period, to about 5 per 10,000 children.

Prevalence of use of Type 1 diabetes medications in that age group increased 106%, to about 2 per 10,000 children.

Similarly, in the 15-19 age group, prevalence of the use of Type 1 diabetes medications increased only 26%, to 6 per 10,000 children and young adults, while prevalence of the use of Type 2 diabetes medications increased 102%, to about 7 per 10,000 children and young adults.

Physicians have been used to thinking of pediatric diabetes as a condition that affects a few children in a population of 100,000 children, not dozens of children in a population of 100,000 children, the Express Scripts researchers note.