Age of onset and type of diabetes.

The age of onset and the clinical type of diabetes mellitus were evaluated on the basis of a cross-sectional study of medical records of 14 municipal health centers in East Finland. Altogether 281 patients were classified as having insulin-dependent (IDDM) and 2713 as having non-insulin-dependent (NIDDM) diabetes. Nearly all patients diagnosed before the age of 19 had IDDM, but a large proportion (37%) of all diagnoses of IDDM were made after that age. Six percent of all diabetic subjects in the age group 15-19 yr were classified as NIDDM and the proportion increased rapidly in older age groups. Half of the patients with NIDDM were diagnosed over the age of 64.