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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)(1990)(1991)(1992)(1993)(1994)(1995)(1996)(1997)(1998) and second (1999)(2000)(2001)(2002)(2003)(2004)(2005)(2006)(2007)(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 -012-2571-8 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.Diabetologia (2012) 55:2142-2147 DOI 10.1007/s00125

Before the onset of late complications, significant excess mortality existed following the diagnosis of type 1 diabetes in childhood, even in recent years. Variation between countries in this excess could not be explained.

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word count: 250 excluding headingsMain text word count: 2,564 including Table and Figure legends Tables and Figures: Tables (2) Methods Twenty-three population-based registers recorded date of diagnosis for new cases of type 1 diabetes among children under 15 years. Tests for seasonal variation in monthly counts aggregated over the 20 year period were conducted. 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 centres with peaks in December to February and relative amplitudes ranging from 11% to 39% (median 18%). However, most centres showed significant departures from a sinusoidal pattern. Pooling results over centres, there was significant seasonal variation in each age-group at diagnosis, with least seasonal variation in those under 5 years. Boys showed greater seasonal variation than girls, particularly those aged 10-14 years. There were no differences in seasonal pattern between four five-year 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/interpretation Seasonality was consistently apparent throughout the period in all age-groups and both sexes, but girls and the under 5s showed less marked variation. Neither sunshine hour nor average temperature data contributed in any substantial way to explaining departures from the sinusoidal pattern.