Increasing incidence of childhood-onset Type I diabetes in 3 Baltic countries and Finland 1983-1998

Aims/hypothesis. We aimed to study the incidence of Type I diabetes in 4 co untries, Estonia, Latvia, Lithuania and Finland, during 1983-1998, focusing on the two separate periods of 1983-1990 and 1991-1998. Methods. Population-based incidence data from nationwide diabetes registrie s were used. Crude and age-standardized incidence rates using the proportio ns of 39%, 32% and 29% for 5-year age groups (0-4,5-9 and 10-14 years) were calculated. Yearly incidence was evaluated and the means between the two p eriods compared. Results. Between 1983-1990 and 1991-1998 there was a statistically signific ant incidence increase in all 4 countries of Estonia, Lativia, Lithuania an d Finland (relative risk 1.15, 95%-Confidence interval 1.10-1.19) and as we ll as in the 3 Baltic states of Estonia, Latvia, Lithuania (relative risk 1 .13. 95%. Confidence interval 1.04-1.22). The crude incidence increased in Estonia from 10.1 (95%-Confidence interval 8.9-11.4) to 12.3 (11.0-13.8), i n Latvia from 6.6 (5.8-7.3) to 7.4 (6.6-8.2) and in Lithuania from 6.8 (6.2 -7.5) to 7.8 (7.1-8.5). In Finland the incidence rose from 34.6 (33.3-36.0) in 1983-1990 to 40.8 (39.4-42.2) in 1991-1998. In children under 5 years o f a age a statistically important increase was seen in Estonia and Finland. The highest incidence for a single year was recorded for all participating countries in the late 1990 s. The highest annual incidence rate of childho od onset Type I diabetes in the world ever known was recorded in Finland in 1998 with 48.5 cases per 100 000 person-years. Conclusion/hypothesis. The incidence of Type I diabetes has increased since 1983 in the three Baltic states as well as in Finland. Long-term monitorin g is needed for a better detection in changes in incidence.