Incidence indicates how often a disease occurs. More precisely, it corresponds to the number of new cases of a disease among a certain group of people for a certain period of time.
Incidence and prevalence of type 1 diabetes in children, 2003
The global incidence of type 1 diabetes in children and adolescents is increasing with an estimated overall annual increase of around 3%1Onkamo P, Vaananen S, Karvonen M, Tuomilehto J. Worldwide increase in incidence of Type I diabetes - the analysis of the data on published incidence trends. Diabetologia 1999; 42(12):1395-1403. 2EURODIAB ACE Study Group. Variation and trends in incidence of childhood diabetes in Europe. Lancet 2000; 355(9207):873-876. 3Green A, Patterson CC. Trends in the incidence of childhood-onset diabetes in Europe 1989-1998. Diabetologia 2001; 44 Suppl 3:B3-B8.. The increase in incidence in type 1 diabetes has been shown in countries having both high and low prevalence with an indication of a steeper increase in some of the low prevalence countries. Several European studies have suggested that, in relative terms, increases are greatest in young children4Tuomilehto J, Virtala E, Karvonen M et al. Increase in incidence of insulin-dependent diabetes mellitus among children in Finland. Int J Epidemiol 1995; 24(5):984-992. 5Gardner SG, Bingley PJ, Sawtell PA, Weeks S, Gale EA. Rising incidence of insulin dependent diabetes in children aged under 5 years in the Oxford region: time trend analysis. The Bart's-Oxford Study Group. BMJ 1997; 315(7110):713-717. 6Dahlquist G, Mustonen L. Analysis of 20 years of prospective registration of childhood onset diabetes time trends and birth cohort effects. Swedish Childhood Diabetes Study Group. Acta Paediatr 2000; 89(10):1231-1237.. Although type 1 diabetes usually accounts for only a minority of the total burden of diabetes in a population it is the predominant form of the disease in younger age groups in most developed countries.
It is estimated that on an annual basis some 65,000 children aged under 15 years develop type 1 diabetes worldwide. Of the estimated total of approximately 430,000 prevalent cases of type 1 diabetes in childhood, more than a quarter come from the South-East Asian (SEA) Region, and more than a fifth from the European (EUR) Region as shown in the figure below. Despite having the largest childhood population, the Western Pacific (WP) Region has the lowest numer of type 1 cases.
Studies have suggested that incidence is not increasing among young adults indicating rather a shift to a younger age at onset. The causes of these changes with time are unknown but the rapidity of the changes and the almost universally increasing trends in younger age groups are unlikely to be due to changes in the genetic background of the disease.
The tables contain information on population size in the 0-14 age group together with estimated numbers of prevalent cases in 2003, organized by region. In those countries for which rates were found in the literature search the following information is given:
The quality of estimates was assessed using the following simple rating system:
A Studies from the country in question that were based on registers that were population based with validated ascertainment levels of 90% or more.
B Other studies from the country in question, provided population denominators were given to enable rates to be calculated (so excluding case-series studies which provided no population denominator).
X Extrapolation using rates from a different country, the identity of the chosen country being indicated.
Further details of methodology and discussion of results are available in the Diabetes Atlas, second edition.