Incidence of childhood onset type 1 diabetes in Western Australia from 1985 to 2016: Evidence for a plateau.

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.