Rapid increase in the incidence of type 1 diabetes in Polish children from 1989 to 2004, and predictions for 2010 to 2025

Abstract

Aims/hypothesis: We analysed the temporal changes in the incidence of childhood type 1 diabetes and its demographic determinants in Poland from 1989 to 2004, validating the model with data from 1970 to 1989. We also estimated a predictive model of the trends in childhood diabetes incidence for the near future.

Methods: Children under 15 years with newly diagnosed type 1 diabetes mellitus and drawn from seven regional registries in Poland were ascertained prospectively using the Epidemiology and Prevention of Diabetes study (EURODIAB) criteria. The type 1 diabetes incidence rates (IRs) were analysed in dependency of age, sex, seasonality, geographical region and population density. Time trends in IR were modelled using several approaches.

Results: The average incidence, standardised by age and sex, for 1989 to 2004 was 10.2 per 100,000 persons per year and increased from 5.4 to 17.7. No difference was found between boys and girls, or between urban and rural regions. In children above 4 years, IR was significantly higher in the population of northern Poland than in that of the country's southern part, as well as in the autumn-winter season, this finding being independent of child sex. Based on the trend model obtained, almost 1,600 Polish children aged 0 to 14 years are expected to develop type 1 diabetes in 2010, rising to more than 4,800 in 2025. The estimates suggest at least a fourfold increase of IR between 2005 and 2025, with the highest dynamics of this increment in younger children.

Conclusions/interpretation: These estimates show that Poland will have to face a twofold higher increase in childhood type 1 diabetes than predicted for the whole European population. The dramatic increase could have real downstream effects on Poland's healthcare system.

Fig. 1

The regions of Poland under investigation, with location and population density

Fig. 2

Circular distribution of type 1 diabetes mellitus incidence. a Overall seasonality in boys and girls aged 0 to 14 years, standardised for age and sex. b Sex-dependent seasonality, boys (black symbols/line) vs girls (grey symbols/line). c Age-dependent seasonality by age group. Black dashed line, age group 0–4 years; grey line, age group 5–9 years; black continuous line, age group 10–14 years. The radius length (a–c) represents the percentage of cases diagnosed on average each month. Irregularity in shape, i.e. departures from circularity, demonstrates the seasonality of incidence

Fig. 3

Estimates of IR. a Estimates, standardised IR, dependent on age groups. b Estimated IR, dependent on sex and age, geographical regions and population density groups. Age groups indicated as above (a); sex-dependent lines are labelled accordingly. c IR dependent on geographical location. Grey line, trend for northern Poland; black line, trend for southern Poland. d Estimated IR for dependence on population density. Grey line, urban areas; black line, rural regions

Fig. 4

Generalised additive model for time trend of type 1 diabetes mellitus incidence, standardised for age and sex, in Poland, 1970 to 2004. Black diamonds, observed cases; black continuous line, generalised additive modelling prediction; light grey circles, observed cases, validation data from Wielkopolskie region; dark grey circles, observed cases, validation data from Łódzkie region

Fig. 5

Prediction of type 1 diabetes mellitus new cases, standardised by age and sex, in Poland, obtained by generalised additive modelling and linear trend models. Grey symbols, predictions obtained with generalised additive modelling; black symbols, predictions obtained by univariate linear model and respective 95% CIs (continuous grey lines)