ArticlesVariation and trends in incidence of childhood diabetes in Europe
Introduction
Type 1 insulin-dependent diabetes is generally believed to be due to an immune destruction of pancreatic β cells in genetically susceptible individuals exposed to environmental risk factors. There has been a rapid increase in the incidence of type 1 diabetes in many European countries in the past few decades.1, 2, 3, 4 This increase, in conjunction with the lack of complete concordance in monozygotic twin pairs,5, 6, 7 points to the importance of environmental factors.
Useful clues about these environmental factors may be obtained by studying geographical variation in incidence in relation to the characteristics of different countries. Fundamental to such analyses are high-quality incidence data uniformly collected via a standard protocol from population-based registers. We have previously reported data for the years 1989–90 from 26 registries in the EURODIAB Study Group, and have established that there is a wide range of incidence rates within Europe.8 The network has since expanded to include 44 registries, with representation from most European countries and Israel. Incidence data for the 6-year period 1989–94 are presented in this paper.
Differences in the trends in incidence between countries or age-groups may also provide important clues about environmental factors. Some recent reports suggest a higher rate of increase among children under 5 years of age compared with the age groups 5–9 and 10–14 years,9, 10 which suggests that the environmental factors responsible for the increase may operate early in life. We address this issue in our analysis of the EURODIAB registry data.
Section snippets
Methods
The establishment of the EURODIAB collaborative group of childhood diabetes registers has been described in detail.8, 11 Briefly, in 1988, prospective registers of new cases of insulin-dependent type 1 diabetes mellitus among children aged under 15 years were established in 26 geographically-defined centres in Europe and Israel. Type 1 diabetes was defined on the basis of a clinical diagnosis of idiopathic diabetes made by a physician. Cases secondary to other conditions (having cystic fibrosis
Average annual incidence rates
Table 1 summarises registration for each centre—the number of cases, the standardised average annual incidence rate, and the estimated completeness of ascertainment. Among the 40 centres validating ascertainment, all but four achieved completeness of ascertainment of over 95%. The estimates for some centres exclude the early years of the study period, but estimates for the years 1989–90 have already been published.8 The standardised rates varied from 3.2 cases per 100 000 per year in the Former
Discussion
This multicentre study shows a greater than 10-fold range in incidence rate of childhood diabetes in Europe. Such variation seems unlikely to be explained by genetic differences, since Europeans (except for some outlying populations) are more homogeneous compared with the indigenous populations of other continents.13 Although the independence of primary and secondary sources of ascertainment cannot easily be verified our assessment of completeness is more thorough than in most previous studies
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