Aims/hypothesis: In Finland, the incidence of Type I (insulin-dependent) diabetes mellitus in children aged 14 years or under is the highest in the world and the trend in incidence has been increasing. Our aim was to determine the most recent trends in incidence and the age distribution at diagnosis of Type I diabetes.
Methods: Data on the incidence of Type I diabetes in Finland nationwide were obtained from two sources: for the period 1965 to 1986 from the Central Drug Registry of the Social Insurance Institution and for the period 1987 to 1996 from the prospective childhood Type I diabetes registry. The annual incidence was calculated per 100,000 people. The increase and the trend in incidence were estimated by fitting the linear regression model with the annual incidence data.
Results: During 1987 to 1993 the incidence of Type I diabetes seemed to be rather stable at 36 per 100,000 per year. The incidence has continued to increase thereafter and reached 45 per 100,000 per year in 1996. The analysis of the long-term trend in incidence between 1965 and 1996 showed an absolute incidence increase of 0.67 per year on average being 3.4 % compared with the incidence in 1965. The increase from 1987 to 1996 was highest in very young children 1-4 years old at diagnosis.
Conclusion/interpretation: The high incidence of Type I diabetes in Finnish children has thus far not levelled off but is increasing further. If the trend continues, the predicted incidence in Finland will be approximately 50 per 100,000 per year in the year 2010.