Time trend of childhood type 1 diabetes incidence in Lithuania and Sweden, 1983-2000

Aim: To compare the time trend of childhood type 1 diabetes over an 18-y period in Lithuania and Sweden - countries with different incidence levels and different socio-economic conditions. Methods: Percent average incidence change per year between 1983 and 2000, based on 8031 Swedish and 1100 Lithuanian cases in the age group 0 - 14 y, was calculated using Poisson regression. Results: Average age- and sex-standardized incidence/100 000/ y was 28.9 (95% CI: 28.2 - 29.5) in Sweden and 7.5 ( 95% CI: 7.1 - 8.0) in Lithuania. Between 1983 and 2000, the average increase per year was 2.2% in Sweden ( 95% CI: 1.7 - 2.6) and 2.3% in Lithuania ( 95% CI: 1.1 - 3.5), but the latter trend depended on an increase during the last few years of the period, and only for girls. In Sweden, incidence increased significantly in all age groups, but more so in the younger groups (3.0%, 2.2% and 1.7% per year in 0 - 4, 5 - 9 and 10 - 14-y age groups, respectively), while in Lithuania a significant increase was found only in the 10 - 14-y age group ( 3.0%). In Sweden, a trend towards a younger age at diagnosis was indicated for both boys and girls when comparing 1983 - 1991 and 1992 - 2000, whereas in Lithuania, the changes in age distribution over time were small, with an opposite tendency for boys. Conclusion: Incidence variability over time differed considerably in the two countries in the region of the Baltic Sea, suggesting a complex effect of environmental risk factors, some of which may be associated with wealth and socio-economic conditions.