The onset age of type 1 diabetes in Finnish children has become younger

OBJECTIVE - To analyze the change in the age distribution at onset of type 1 diabetes in buys and girls aged 1-14 years during a 32-year period (from 1965 to 1996). RESEARCH DESIGN END METHODS - Data on the incidence of type 1 diabetes in F inland 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 co mpare the trends between the various age-groups (lif, 5-9, and 10-14 years) and sexes. RESULTS - The incidence of type 1 diabetes increased predominantly in the y ounger age-groups. In children aged 1-4 years, the increase was 4.2% per ye ar, 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, a nd 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 a ged 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 lear). CONCLUSIONS - The greatest increase in the incidence of type 1 diabetes mai nly occurred in children aged <5 years. The incidence in young boys has bee n increasing since the mid-1960s, whereas in young girls, the significant i ncrease began later, around the mid-1970s. In children aged 10-14 years, th e increase in incidence has leveled off.