Identification of the Cohort of Type 1 Diabetes Presenting in Lombardy in 1983–84: a Validated Assessment

An incidence register for Type 1 diabetes was started in Lombardy in 1983–84 for people under 35 years of age. The main information source was the Regional Health Service record system, which provides anonymous reports on all patients discharged from public and private hospitals. Great care was taken to assure the quality of the data in the register. The clinical diagnosis was validated by examining the case notes. Completeness of the register was assessed using multiple independent sources of case ascertainment such as the list of the Youth Diabetics Association, the files of three hospital endocrinology centres, and the registry of conscripts rejected because of diabetes. The estimated age‐adjusted (world standard) annual incidence rate was 6.04 per 100 000 in the group 0–18 years and 5.96 per 100 000 in the age group 0–14 years. Females had peak incidence at 11 years of age, males had peak incidence 2 years later. These results confirm the low occurrence of Type 1 diabetes in northern Italy. A seasonal variation in onset of Type 1 diabetes was seen.