To investigate the role of genetic and environmental factors in the pathogenesis of type 1 diabetes mellitus (T1D), we carried out a study in Germany aimed at comparing the prevalence and incidence of T1D among children of migrant Italians from high-risk (Sardinia) and low-risk (continental Italy) regions versus German children. Children from Italy were identified by the "Baden-Wuerttemberg (BW) Diabetes Incidence Registry", which registered 4017 newly diagnosed T1D patients, aged 0-14 years, between 1987 and 2003. Data relating to T1D children from Sardinia were elicited from more than 2000 questionnaires. Our findings were: (1) T1D is more frequent among German children than among children of Italian migrants [incidence rate (IR) 14.8/100,000/year, 95% confidence interval (CI) 14.4-15.4 vs. IR 10.8/100,000/year, 95% CI 8.2-13.6); (2) the incidence of T1D among Italian children residing in Germany is similar to that of Italian children in the home country (IR 10.8/100,000/year, 95% CI 8.2-13.6 vs. 8.4/100,000/year, 95% CI 7.9-8.9); (3) the prevalence of T1D among Sardinian children is higher than that among German children (0.11%, 95% CI 0.11-0.12) independent of the place where the Sardinian children are living (Sardinian children in Germany 2.3%, 95% CI 0.5-6.5 vs. Sardinian children in Sardinia 0.30%, 95% CI 0.27-0.32).
Conclusion: Children from high- and low-risk areas of Italy have incidence rates of T1D that are closer to those of their native regions than to those of German children, indicating that genetic factors play a predominant role in the pathogenesis of T1D.