Bayesian analysis of geographical variation in the incidence of Type I diabetes in Finland.
OBJECTIVE
In Finland, the incidence of Type I (insulin-dependent) diabetes mellitus among children aged 14 years or under is the highest in the world. The increase in incidence is approximately 3% per year. A marked geographical variation in incidence was reported in Finland during the late 1980s. Our aim was to explore the most recent regional pattern in incidence of Type I diabetes in Finland.


METHODS
Data on the nationwide incidence of childhood diabetes in Finland was obtained from the Prospective Childhood Diabetes Registry for the periods 1987-1991 and 1992-1996. Population data was obtained from the National Population Registry. The geographical pattern of incidence was studied applying a Bayesian hierarchical approach and Geographical Information Systems. The inferences from the data was based on the estimated geographical intensity of diabetes.


RESULTS
There was a clear evidence of geographic variation for the risk of childhood diabetes during the entire 10-year period. The high-risk areas were found in the wide belt crossing the central part of Finland. Comparison of the estimated intensity of diabetes between the two 5-year periods showed that the geographical pattern of diabetes risk has changed over time. Our analyses also confirmed the existence of a few persistent high-risk and low-risk areas in Finland.


CONCLUSIONS
The finding of high-risk areas of childhood Type I diabetes suggests that specific genetic or environmental risk factors have become greater in certain geographic locations in Finland.
Rytkönen
M
M
National Public Health Institute, Department of Epidemiology and Health Promotion, Helsinki, Finland.
Ranta
J
J
Tuomilehto
J
J
Karvonen
M
M
D000293:Adolescent; D001499:Bayes Theorem; D002648:Child; D002675:Child, Preschool; D003922:Diabetes Mellitus, Type 1 / Q000453:epidemiology*; D005260:Female; D005387:Finland / Q000453:epidemiology; D005843:Geography; D006801:Humans; D015994:Incidence; D007223:Infant; D008297:Male; D012042:Registries; D015203:Reproducibility of Results