Type 1 diabetes among Sardinian children is increasing - The Sardinian diabetes register for children aged 0-14 years (1989-1999)

OBJECTIVE - The Sardinian type 1 diabetes register represented the basis to determine the most recent trends and the age distribution of type 1 diabetes incidence among Sardinians <15 years of age during 1989-1999. Part of the data (1989-1998) has been already published by the EURODIAB Group with a lower completeness of ascertainment (87%). The geographical distribution of type 1 diabetes risk was also investigated. RESEARCH DESIGN AND METHODS - The new cases of type 1 diabetes in children aged 0-14 years in Sardinia were prospectively registered from 1989 to 1999 according to the EURODIAB ACE criteria. The completeness of ascertainment calculated applying the capture-recapture method was 91%. Standardized incidence rates and 95% CI were calculated assuming the Poisson distribution. Trend of type 1 diabetes incidence was analyzed using the Poisson regression model. Maps of the geographical distribution of type 1 diabetes risk for the whole Lime period and separately for 1989-1994 and 1995-1999 were produced applying a Bayesian method. RESULTS - A total of 1,214 type 1 diabetic patients were registered yielding to an overall age- and sex-standardized incidence rate of 38.8/100,000 (95% CI 36.7-41.1). There was a male excess with an overall male-to-female ratio of 1.4 (1.3-1.8). The increase of incidence during the 11 years analyzed was statistically significant, (P = 0.002) with a yearly increasing rate of 2.8% (1.0-4.7). No evidence of an effect of age and sex on this trend has been found. The geographical distribution of type 1 diabetes relative risk (RR) showed that the highest risk areas are located in the Southern and central-eastern part of the island and the lowest risk in the northeastern part, even if most of these differences were not statistically significant. This geographical distribution seemed to remain mainly the same between 1989-1994 and 1995-1999. CONCLUSIONS - The homogeneity of diabetes risk and the increase of incidence over the age-groups in the Sardinian population stress the role of an environmental factor Uniformly distributed among the genetically high-risk Sardinians.