Increased risk of childhood type 1 diabetes in children born after 1985.
OBJECTIVE
The incidence rate of childhood type 1 diabetes is thought to be increasing; however, Danish studies have not confirmed this. Using a national diabetes register initiated in 1996 and two previous regional incidence studies, we studied the age-specific incidence of type 1 diabetes over 30 years. Here, we describe the incidence rates of type 1 diabetes in Danish children from 1996 to 2000 and evaluate trends in age-specific incidence rates from 1970 to 2000.


METHODS
A nationwide registration of all newly diagnosed cases of type 1 diabetes among children under the age of 15 years was established in Denmark in 1996. Incidence rates of type 1 diabetes in Denmark were obtained from this register. Age-specific incidence rates were compared with data collected from 1970 to 1976 and from 1980 to 1984, both population-based studies using existing national routine registration of hospitalizations within the survey areas. Population data were obtained from Statistics Denmark.


RESULTS
During the study period, 1,421 Danish children developed type 1 diabetes before the age of 15 years. The incidence rates by age-groups were: 12.7, 19.4, and 26.3 for the 0-4, 5-9, and 10-14 years age-groups, respectively, and 19.5 for the 0-14 years age-group per 100,000 in the period 1996-2000. An age-period-cohort analysis showed a modest drift effect (yearly increase) of 1.2% (0.7-1.8) from 1970 to 2000, and a significant birth cohort effect with an increased risk for children born after 1985 was observed.


CONCLUSIONS
The incidence rate of type 1 diabetes is rising in children living in Denmark. The steep increase in the youngest age-group was explained by the increased risk for cohorts born at the beginning of the 1980s.
Svensson
Jannet
J
Steno Diabetes Centre, Gentofte, Denmark. jasv@novonordisk.com
Carstensen
Bendix
B
Mølbak
AnneGrete
A
Christau
Bjørn
B
Mortensen
Henrik B
HB
Nerup
Jørn
J
Borch-Johnsen
Knut
K
D000293:Adolescent; D017677:Age Distribution; D000367:Age Factors; D002648:Child; D002675:Child, Preschool; D015331:Cohort Studies; D003718:Denmark / Q000453:epidemiology; D003922:Diabetes Mellitus, Type 1 / Q000453:epidemiology*; D004641:Emigration and Immigration; D005260:Female; D006801:Humans; D015994:Incidence; D007223:Infant; D008297:Male; D015233:Models, Statistical; D012042:Registries; D012307:Risk Factors