To compare nationwide incidence of childhood insulin-dependent diabetes mellitus (IDDM) in children aged 0-14 yr between Estonia and Finland during 1980-1988. For Estonia, which has a population genetically and linguistically related to Finland, only limited information was available. Finland has the highest incidence of IDDM in the world.
The registration of all new cases of IDDM in Estonia was conducted by the local district pediatricians who reported every newly diagnosed diabetic patient to the Republic Endocrinology Centre. Registration of all new cases of IDDM in Finland was based on the statistics of the Social Insurance Institution, which approves free-of-charge insulin treatment for diabetes. These data were validated with one or more additional data sources. The case ascertainment rate approached 100% in both countries.
The average yearly incidence of IDDM standardized for age for the years 1980–1988 in Estonia was ~ 33% of that in Finland. Among males it was 11.3 (95% confidence interval [CI] 10.3–12.3) per 100,000 in Estonia and 35.1 (95% CI 33.4–36.9) per 100,000 in Finland, and among females 10.1 (95% CI 9.2–11.1) per 100,000 in Estonia and 30.4 (95% CI 28.8–32.1) per 100,000 in Finland. When the two periods 1980–1982 and 1986–1988 were compared, the age-standardized incidence in Estonia remained unchanged, whereas in Finland it increased ~ 20%.
The data between two populations who are ethnically and linguistically similar and live geographically close but in a different environment, provides further evidence that both genetic and environmental factors are contributing to the risk of IDDM.