Changing geographical distribution of diabetes mellitus type 1 incidence in Austrian children 1989--2005

Abstract

Objectives: We investigated whether the significant spatial West/East trend of incidence of Diabetes mellitus Type 1 in Austrian children changed between 1989 and 2005. Additionally we tested, whether population density and mean body mass index of newborns is associated with incidence.

Study design and setting: All newly diagnosed cases aged 0-14 years in Austria (n = 2644), prospectively registered from 1989 to 2005 were allocated to 99 districts. Ecological regression and analysis was done by Bayesian hierarchical models including spatially correlated risks.

Results: In Austria, the incidence rose from 9.1/100.000 in 1989--1994 to 14.9/100.000 in 2001--2005. The spatial trend in the period 1989--1995, showing high incidence in the Eastern parts of Austria, disappeared. In the period 2001--2005 a significant inverse negative association of population density with incidence was found. Mean body mass index of newborns in the Austrian population is significantly positively associated with incidence.

Conclusion: The observation of higher incidence in rural areas in Austria during recent years may reflect a lower exposure to protective environmental factors, e.g. infections early in life. The observed association with the BMI in newborns indicates that neonatal or prenatal metabolic aspects may modulate the risk for childhood diabetes. We cannot explain the change in the spatial distribution of incidence.