Abstract
Aims/hypothesisAgainst a background of a near-universally increasing incidence of childhood type 1 diabetes, recent reports from some countries suggest a slowing in this increase. Occasional reports also describe cyclical variations in incidence, with periodicities of between 4 and 6 years.MethodsAge/sex-standardised incidence rates for the 0- to 14-year-old age group are reported for 26 European centres (representing 22 countries) that have registered newly diagnosed individuals in geographically defined regions for up to 25 years during the period 1989–2013. Poisson regression was used to estimate rates of increase and test for cyclical patterns. Joinpoint regression software was used to fit segmented log-linear relationships to incidence trends.ResultsSignificant increases in incidence were noted in all but two small centres, with a maximum rate of increase of 6.6% per annum in a Polish centre. Several centres in high-incidence countries showed reducing rates of increase in more recent years. Despite this, a pooled analysis across all centres revealed a 3.4% (95% CI 2.8%, 3.9%) per annum increase in incidence rate, although there was some suggestion of a reduced rate of increase in the 2004–2008 period. Rates of increase were similar in boys and girls in the 0- to 4-year-old age group (3.7% and 3.7% per annum, respectively) and in the 5- to 9-year-old age group (3.4% and 3.7% per annum, respectively), but were higher in boys than girls in the 10- to 14-year-old age group (3.3% and 2.6% per annum, respectively). Significant 4 year periodicity was detected in four centres, with three centres showing that the most recent peak in fitted rates occurred in 2012.Conclusions/interpretationDespite reductions in the rate of increase in some high-risk countries, the pooled estimate across centres continues to show a 3.4% increase per annum in incidence rate, suggesting a doubling in incidence rate within approximately 20 years in Europe. Although four centres showed support for a cyclical pattern of incidence with a 4 year periodicity, no plausible explanation for this can be given.
Highlights
The increasing incidence of childhood type 1 diabetes has been well documented both in Europe, with an estimated annual increase of 3.9% during the period 1989–2003 [1], and worldwide, with an estimated annual increase of 2.8% in the period 1990–1999 [2]
Our analyses of individual centre results confirmed the recent slowing of incidence rate increases in some high-incidence
In the majority of centres, a steady log-linear increase in rates with time provided a good description of the temporal changes, with only a few areas showing some evidence of non-uniformity
Summary
The increasing incidence of childhood type 1 diabetes has been well documented both in Europe, with an estimated annual increase of 3.9% (95% CI 3.6%, 4.2%) during the period 1989–2003 [1], and worldwide, with an estimated annual increase of 2.8% (95% CI 2.4%, 3.2%) in the period 1990–1999 [2]. In the USA, pooled data from five centres for children and adolescents under 20 years of age indicated a 1.8% (95% CI 1.0%, 2.6%) annual increase during 2002–2012 after adjustment for age, sex and race or ethnic group [3], and a similar rate of increase of 1.3% (95% CI 0.0%, 2.5%) has been reported for the Canadian province of British Columbia in the period 2002–2013 [4]. A report from Zhejiang province in the low-incidence region of China described a very rapid 12.0% (95% CI 7.6%, 16.6%) increase in annual incidence rate among those aged under 20 years during the period 2007–2013 [9]
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