Melitta,
Allow me to clarify. When I said that newly-dx'ed young adults withT1 are not the "norm", what I meant is that withing the entire population of people with diabetes, young adults (17-30) newly dx'ed with t1 constitute a small portion of that population. That is, if you took all 23.6 million US diabetics out there, only a tiny portion of them would have met the qualifications to participate in the DCCT. Anyone who has had a decent research methods class could list the problems with using such an unrepresentative sample, the most important of which is that the results cannot be easily generalized to groups of individuals that vary in one or more important ways from the group studied. Doctors did try to extend the DCCT results to groups that weren't studied, such as children and the elderly, and when they did, they found maintaining "tight control" to be even more difficult than it was with the "standard" young adult.
As reported in The International Handbook of Diabetes Mellitus, 1:300 children and 1:100 adults will be diagnosed with diabetes at some point in their lives, so yes, you are right and more adults are dx'ed with T1 dm than children are.