Middle-aged and older adults are still at the highest risk for developing type 2 diabetes. According to the CDC, there were a total of 1.7 million new total diabetes cases in 2012. In 2012, adults aged 45 to 64 were the most diagnosed age group for diabetes. New cases of both type 1 and type 2 diabetes in people 20 years and older were distributed like this: 1  ages 20-44: 371,000 new cases.  ages 45-64: 892,000 new cases.