Incidence of diabetes mellitus among children of Italian migrants substantiates the role of genetic factors in the pathogenesis of type 1 diabetes

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.