For years doctors have warned of a rising epidemic of diabetes among children. Yet there has been surprisingly little firm data on the extent of this disease among younger Americans.

Now a nationally representative study has confirmed that from 2001 to 2009 the incidence of Type 1 and Type 2 diabetes drastically increased among children and adolescents across racial groups.

The prevalence of Type 1 diabetes increased 21 percent among children up to age 19, the study found. The prevalence of Type 2 diabetes among those ages 10 to 19 rose 30 percent during the period.

Those are “big numbers,” said Dr. Robin S. Goland, a co-director of the Naomi Berrie Diabetes Center at Columbia University Medical Center in New York, who has been in practice for about 25 years. “In my career, Type 1 diabetes was a rare disease in children, and Type 2 disease didn’t exist. And I’m not that old.”