The global increase in the incidence of type 1 diabetes in children and adolescents is widely recognised, although considerable variability has been observed among countries [11
]. Scandinavia has one of the highest IRs of childhood diabetes, although variability is high, both between and even within different countries [4
]. Increasingly often, moreover, type 1 diabetes is being observed in patients with low genetic susceptibility [13
]. Environmental factors therefore seem to represent a major trigger, initiating the disease by their sequential or simultaneous influence and/or due to lack of protective environmental agents [14
Epidemiological studies conducted in the 1980s and early 1990s, such as EURODIAB and the Diabetes Mondiale Project (DIAMOND), ranked Poland among countries of very low type 1 diabetes incidence, with approximately 6.6 cases per 100,000 persons per year [2
]. Current studies [8
] indicate considerable change in this classification, grouping Poland with countries that have medium type 1 diabetes incidence, i.e. above 15 cases per 100,000 persons per year.
The dynamic increase in new cases of type 1 diabetes in Central and Eastern Europe has been reported recently by various investigator teams [2
]. Thus in the EURODIAB study [4
], which covered 1989 to 2003, Poland was represented by the Silesian region, with a mean maximal increase in IR of 9.3% per year. Similar results were found for other Eastern European states: Romania (8.4% increase), the Czech Republic (6.7% increase) and Slovakia (5.1% increase in diabetes incidence). By contrast, countries traditionally experiencing high type 1 diabetes incidence, such as Finland, Sweden and Norway, showed more modest increases of only 2.7%, 3.3% and 1.3%, respectively.
This dramatic increase of new cases in the countries named could be associated with their rapid adoption of a westernised lifestyle after the socioeconomic transformations seen since the early 1990s [22
]. The most important factors connected with this process are, in our opinion: the wide availability of pre-processed food, the popularisation of fast-food and lifestyle-related changes in leisure activities, e.g. computer/internet and media player use instead of natural physical activity. These and similar factors have probably caused the twofold increase in prevalence of overweight and obesity among Polish children [24
]. The predicted incidence of type 1 diabetes in Polish children and adolescents in the next 15 years is alarming. A validated statistical model enabled us to reliably predict that from 2010 to 2025 the number of new cases would reach 46,600, with an evident downward shift in the age of onset.
The model established in this study confirms previous observations of a most remarkable rise in childhood type 1 diabetes incidence among the youngest age groups [25
]. Thus the number of children who will not even remember their pre-diabetes life, without insulin dependence, is rising. Likewise, the impact of prognostic factors that strongly contribute to chronic diabetic complications, e.g. disease duration and its influence on the psychosocial development of a child and his/her family, is being extended.
In some regions, sex-related differences have been reported in selected age subgroups [27
]. Our analysis of the Polish population revealed a similar distribution of new cases in both sexes, with no changes forecast for the following years. The north–south gradient in type 1 diabetes incidence, with a higher disease frequency in the northern regions, has been previously described [4
]. This type of incidence distribution was also observed by us in Poland. However, future predictions indicate that an inverse trend may emerge in the coming years. This apparent inversion might be explained by a rapid increase in type 1 diabetes incidence across the whole country. Another factor worth considering is the relatively small distance between the studied regions, 400 km on average.
While progressive urbanisation might be a contributory factor to the increased type 1 diabetes incidence, the data on this subject remain inconsistent [27
]. Our analysis did not reveal significant differences between urban and rural areas, although a slightly higher incidence was noted in areas characterised by more dense populations, this being particularly visible in the proposed predictive model.
The estimate of the increase in type 1 diabetes does not seem to be influenced by changes in identification of cases. This has remained high and stable throughout the past five decades, due to the Polish healthcare system. All children with diabetes remain under the care of paediatric diabetes centres.
A recent report by the DIAMOND group on seasonality in type 1 diabetes incidence demonstrates that, in some regions of the world (40% of all participating centres), winter or summer peaks are discernible, depending on the geographic coordinates of the country [29
]. These relations seem particularly true for countries more distant from the equator, countries with higher IR and among older children. In our study, apart from the youngest subgroup, the seasonality of type 1 diabetes incidence is clearly visible, with the highest emergence of new cases during the autumn and winter months. Plausible explanations for this phenomenon usually focus on the higher incidence of viral and bacterial infections at this time of the year [16
]. In contrast, infectious morbidity in the youngest children is less season-dependent, which might be reflected in this long-term observation. Another explanation of the seasonal rise in type 1 diabetes may be related to the increased physical activity and lack of school stress during the summer holiday [29
Our study has several limitations. It covers only 35% of the childhood diabetes population, the result of Poland not having a national diabetes register. Our regional registers include only patients up to 14 years of age, because the healthcare system allows patients from the age of 16 years to decide whether to stay in paediatric care or move to adult care. Additionally, only a limited number of functional dependences could be investigated during model building and the obtained estimates should be treated with some caution. It seems reasonable that the process of IR increase will not follow exponential-like growth, but will reach some saturation level in the future. To be able to detect that level, the data must include the symptoms of such a process. However, the incidence of type 1 diabetes in Poland is still growing rapidly, thereby making such detection impossible. The prediction obtained for 2025 classes Poland with countries that have an IR equal to 75 cases per 100,000 persons per year, a value comparable to the predictions for Scandinavian countries [31
]. As predictions made more than a few years ahead can prove to be very inaccurate, it should be kept in mind that the conclusion on the possible rapid rise of type 1 diabetes mellitus cases is not definite.
During the past 15 years the incidence of childhood type 1 diabetes in Poland has increased threefold, with a predicted additional at least fourfold increase from 2005 to 2025, with the highest dynamics of this increment in the youngest age group. These estimates show that Poland will have to face a twofold higher increase in childhood type 1 diabetes than that predicted for the whole European population. The EURODIAB data published in 2009 forecast only a less than twofold increase in new cases (until 2020), with the same incidence trend among younger and very young children [4
While 12,465 cases were diagnosed in Poland from 1989 to 2004, more than 46,600 cases are expected in the following 16 years. The burden of childhood diabetes will therefore increase dramatically, with clear downstream effects on the country’s healthcare system.