OBJECTIVE: To determine the incidence of childhood type 1 diabetes mellitus (T1D) in Western Australia from 2011 to 2016, and to examine the temporal trends between 1985 and 2016.
METHODS: An observational cohort study was undertaken of all children newly diagnosed with T1D aged 0 to 14 years in Western Australia from 1985 to 2016. Cases were identified from the Western Australian Children's Diabetes Database, a population-based diabetes register previously estimated to be >99% complete. Annual age-standardized and age- and sex-specific incidence rates were calculated and the Joinpoint Regression Program used to identify any significant changes in trends over the study period.
RESULTS: A total of 2499 cases were included (1272 boys, 1227 girls). The overall mean annual incidence was 19.1/100 000 person years (95% confidence interval, CI: 18.3-19.8), with no significant difference found between boys and girls. The mean annual incidence of 12.1/100 000 person years (95% CI: 11.1-13.1) in 0 to 4-years was significantly lower than that observed in 5 to 9 (21.6/100 000 [95% CI: 20.2-23.0]) and 10 to 14 (23.5/100 000 [95% CI: 22.1-25.0]) years. Joinpoint regression analysis identified a significant change in the temporal trend occurring in 2003. From 1985 to 2003, the incidence increased on an average of 3.3% per year (95% CI: 1.9-4.7). However, from 2003 to 2016, no significant change in the temporal trend occurred (-0.6% per year [95% CI: -2.4-1.2]).
CONCLUSIONS: This study provides evidence for a possible plateauing in the incidence of childhood T1D in Western Australia, following a peak in 2003. Ongoing monitoring of the incidence will be essential to determine how temporal trends continue to evolve.