Cyclical Variation in the Incidence of Childhood Type 1 Diabetes in Western Australia (1985-2010)

OBJECTIVE: To examine the incidence of childhood type 1 diabetes in Western Australia from 1985-2010. RESEARCH DESIGN AND METHODS: Incidence rates were calculated for children aged 0-14 years and were analyzed by calendar year, sex, and age at diagnosis. RESULTS: There were 1,873 cases, and the mean incidence was 18.1/100,000 person-years (95% CI: 17.5-19.2). The incidence increased by 2.3% a year (1.6-2.9%) with a sinusoidal 5-year cyclical variation of 14% (7-22%). The lowest rate of increase in incidence was observed in 0-4-year-olds. CONCLUSIONS: The cyclical pattern in incidence observed supports the role of environmental factors in childhood type 1 diabetes.