Seasonal variation in month of diagnosis in children with type 1 diabetes registered in 23 European centers during 1989-2008: little short-term influence of sunshine hours or average temperature.

BACKGROUND: The month of diagnosis in childhood type 1 diabetes shows seasonal variation. OBJECTIVE: We describe the pattern and investigate if year-to-year irregularities are associated with meteorological factors using data from 50 000 children diagnosed under the age of 15 yr in 23 population-based European registries during 1989-2008. METHODS: Tests for seasonal variation in monthly counts aggregated over the 20 yr period were performed. Time series regression was used to investigate if sunshine hour and average temperature data were predictive of the 240 monthly diagnosis counts after taking account of seasonality and long term trends. RESULTS: Significant sinusoidal pattern was evident in all but two small centers with peaks in November to February and relative amplitudes ranging from ± 11 to ± 38% (median ± 17%). However, most centers showed significant departures from a sinusoidal pattern. Pooling results over centers, there was significant seasonal variation in each age-group at diagnosis, with least seasonal variation in those under 5 yr. Boys showed greater seasonal variation than girls, particularly those aged 10-14 yr. There were no differences in seasonal pattern between four 5-yr sub-periods. Departures from the sinusoidal trend in monthly diagnoses in the period were significantly associated with deviations from the norm in average temperature (0.8% reduction in diagnoses per 1 °C excess) but not with sunshine hours. CONCLUSIONS: Seasonality was consistently apparent throughout the period in all age-groups and both sexes, but girls and the under 5 s showed less marked variation. Neither sunshine hour nor average temperature data contributed in any substantial way to explaining departures from the sinusoidal pattern.

Trends in childhood type 1 diabetes incidence in Europe during 1989-2008: evidence of non-uniformity over time in rates of increase.

AIMS/HYPOTHESIS: The aim of the study was to describe 20-year incidence trends for childhood type 1 diabetes in 23 EURODIAB centres and compare rates of increase in the first (1989-1998) and second (1999-2008) halves of the period. METHODS: All registers operate in geographically defined regions and are based on a clinical diagnosis. Completeness of registration is assessed by capture-recapture methodology. Twenty-three centres in 19 countries registered 49,969 new cases of type 1 diabetes in individuals diagnosed before their 15th birthday during the period studied. RESULTS: Ascertainment exceeded 90% in most registers. During the 20-year period, all but one register showed statistically significant changes in incidence, with rates universally increasing. When estimated separately for the first and second halves of the period, the median rates of increase were similar: 3.4% per annum and 3.3% per annum, respectively. However, rates of increase differed significantly between the first half and the second half for nine of the 21 registers with adequate coverage of both periods; five registers showed significantly higher rates of increase in the first half, and four significantly higher rates in the second half. CONCLUSIONS/INTERPRETATION: The incidence rate of childhood type 1 diabetes continues to rise across Europe by an average of approximately 3-4% per annum, but the increase is not necessarily uniform, showing periods of less rapid and more rapid increase in incidence in some registers. This pattern of change suggests that important risk exposures differ over time in different European countries. Further time trend analysis and comparison of the patterns in defined regions is warranted.

Incidence and trends of childhood Type 1 diabetes in Croatia from 1995 to 2003.

AIMS/HYPOTHESIS: The aim of this study was to examine incidence and trends of Type 1 diabetes in children aged 0-14 years in Croatia from 1995 to 2003. METHODS: The incidence data were obtained from two sources. The incidence was calculated as the number of newly diagnosed Type 1 diabetes patients per 100,000 person-years for the age group 0-14 years, and subgroups 0-4, 5-9, and 10-14 years. Standardized incidence was calculated using the method of direct standardization to the world standard population for the age group 0-14 years. The ascertainment was estimated with capture-recapture method. Trends in the incidence of Type 1 diabetes for period from 1995 to 2003 in Croatia were analyzed using Poisson regression model. RESULTS: The standardized incidence of Type 1 diabetes for the whole age group was 8.87 per 100,000 person-years (95% CI: 5.07-12.68), for girls 8.47 (95% CI: 7.54-9.41) and for boys 9.26 (95% CI: 8.30-10.21). During the studied period, the trend in incidence raised significantly for the whole age group (chi(2)=32.6, p<0.001). The average annual increase in incidence was 9% (95% CI: 5.8-12.2). CONCLUSIONS/INTERPRETATION: This rate of incidence places Croatia in a group of countries with moderate risk for development of Type 1 diabetes. The average annual increase in incidence of 9% is markedly higher than in most European countries, and probably reflects lifestyle changes upon economic recovery of the country.