The onset age of type 1 diabetes in Finnish children has become younger. The Finnish Childhood Diabetes Registry Group.
OBJECTIVE
To analyze the change in the age distribution at onset of type 1 diabetes in boys and girls aged 1-14 years during a 32-year period (from 1965 to 1996).


METHODS
Data on the incidence of type 1 diabetes in Finland were obtained from the Central Drug Registry of the Social Insurance Institution for 1965-1986 (6,195 cases) and from the Prospective Childhood Diabetes Registry for 1987-1996 (3,613 cases). The change in age- and sex-specific incidence was estimated by fitting the linear regression with the logarithm of the annual incidence data. Analysis of variance was used to compare the trends between the various age-groups (1-4, 5-9, and 10-14 years) and sexes.


RESULTS
The incidence of type 1 diabetes increased predominantly in the younger age-groups. In children aged 1-4 years, the increase was 4.2% per year, and the overall 32-year relative increase was 338%. For children aged 5-9 and 10-14 years, the increase was 2.5 and 1.3% per year, respectively, and the overall relative increase was 116 and 49%, respectively. In boys aged 1-9 years, the increase was greatest from 1965 to 1984, whereas in girls aged 1-9 years, the statistically significant increase occurred between 1985 and 1996. In children aged 10-14 years, the only significant increase was seen in boys from 1965 to 1974 (3.7% per year).


CONCLUSIONS
The greatest increase in the incidence of type 1 diabetes mainly occurred in children aged < 5 years. The incidence in young boys has been increasing since the mid-1960s, whereas in young girls, the significant increase began later, around the mid-1970s. In children aged 10-14 years, the increase in incidence has leveled off.
Karvonen
M
M
Department of Epidemiology and Health Promotion, National Public Health Institute, Helsinki, Finland. marjatta.karvonen@ktl.fi
Pitkäniemi
J
J
Tuomilehto
J
J
D000293:Adolescent; D000367:Age Factors; D017668:Age of Onset; D002648:Child; D002675:Child, Preschool; D003922:Diabetes Mellitus, Type 1 / Q000453:epidemiology*; D005260:Female; D005387:Finland / Q000453:epidemiology; D006801:Humans; D015994:Incidence; D007223:Infant; D008297:Male; D012044:Regression Analysis; D012737:Sex Factors; D013997:Time Factors