To provide reliable data on the incidence of IDDM in Sardinia and contribute to a better understanding of its geographical variability throughout Europe.
All newly diagnosed cases of IDDM with onset < 30 yr of age between 1 January 1989 and 31 December 1990 among residents in Sardinia were recorded. Primary ascertainment was based on notification by all Sardinian hospitals, outpatient clinics, family doctors, and pediatricians. The local IDDM patient association served as the secondary and independent source.
The completeness of ascertainment was 92.8%. The annual incidence rate of IDDM (per 100,000) over the 2-yr period was 30.7 in the 0–14–yr-old age-group and 24.1 in the entire 0–29–yr-old range, respectively, with no significant differences between the two groups. Male/female ratios were 1.25 and 1.55, respectively. No significant seasonal variation in incidence was observed.
Sardinia appears to have the second-highest IDDM incidence rate in Europe after Finland, and the island contradicts the generally accepted rule of a south-to-north incidence gradient.