Descriptive Epidemiology of IDDM in Hokkaido, Japan: The Childhood IDDM Hokkaido Registry

OBJECTIVE To identify the incidence of IDDM with regard to sex, age, family history of diabetes, season, and 5-year period of childhood IDDM among children ages 0–14 years from a population-based epidemiological study in Hokkaido, Japan, from 1973 to 1992.

RESEARCH DESIGN AND METHODS Registration of all new IDDM cases in Hokkaido was conducted by the Childhood IDDM Hokkaido Registry Study Group from 1973 to 1992. The cases were selected from among 1) patients who were admitted to the member hospitals of the study group, 2) patients who answered a questionnaire distributed to hospitals and diabetic clinics throughout Hokkaido, and 3) patients whose cases were recorded in free-treatment medical records of urban and rural districts. The case ascertainment rate was estimated to be 100%. Differences in incidence with regard to sex, age, family history of diabetes, season, and year period were analyzed by the Poisson regression analysis by GENMOD.

RESULTS During the 20-year period studied, 396 cases (181 boys, 215 girls) of abruptonset IDDM were registered. Statistically significant differences in annual incidence were found according to sex (female), age (8–14 years), history (having no diabetes in family), season (spring), and 5-year period.

CONCLUSIONS This is the first population-based, long-term epidemiological study of childhood IDDM from Japan. We observed a significantly higher annual incidence (per 100,000/year) of IDDM in female subjects (1.81), older age-groups (2.25 for 8–14 years), subjects with no family history of diabetes (1.26), diabetes onset in the spring (2.20), and an increased trend over the 20 years. In addition, the heterogeneity of IDDM among Japanese children needs to be elucidated.