Incidence and prevalence rates of diabetes mellitus in Italy from routine data: a methodological assessment

This study was undertaken to identify and validate possible existing sources of information to estimate the prevalence of known diabetes and the incidence of Type 1 (insulin-dependent) diabetes in Italy. The prevalence of known diabetes was estimated on the basis of data on drug sale, using specific defined daily doses as index of drug consumption. The estimation of the average daily dose used for calculations was carried out on a consecutive series of 911 diabetic subjects from two outpatient clinics. The incidence of Type 1 (insulin-dependent) diabetes was obtained by processing data routinely collected by the Regional Health Services, related to hospital discharge diagnosis records mentioning diabetes mellitus. The validation was carried out in 12 hospitals of the same Region. The estimated prevalence rate of known diabetes was 1.7%, including patients on dietary treatment. In the Lombardia Region in 1982-83 the estimated annual average incidence of Type 1 (insulin-dependent) diabetes, under the age of 35 was 4.6/100,000. This rate appears much lower then that observed in Northern Europe and the United States while it is similar to the French rate. This is in agreement with the findings of studies showing changes with latitude of the incidence rates of Type 1 (insulin-dependent) diabetes.