Continued increase in the incidence of childhood Type 1 diabetes in a population-based Australian sample (1985-2002)

Abstract

Aims/hypothesis. Our aim was to determine the incidence of Type 1 diabetes in children who were 0 to 14 years of age in Western Australia from 1985 to 2002, and to analyse the trends in incidence rate over the same period. Methods. Primary case ascertainment was from a prospective population-based diabetes register that was established in 1987, and secondary case ascertainment was from the Western Australia Hospital Morbidity Data System. Denominator data were obtained from the Australian Bureau of Statistics. Poisson regression was used to analyse the incidence rates by calendar year, sex and age at diagnosis. Results. There was a total of 1144 cases (560 boys, 584 girls). Using the capture-recapture method, case ascertainment was estimated to be 99.8% complete. The mean age standardised incidence from 1985 to 2002 was 16.5 per 100000 person years (95% CI 14.7-18.2), ranging from 11.3 per 100000 in 1985 to 23.2 per 100000 in 2002. The incidence increased on average by 3.1% (95% CI 1.9%-4.2%) a year over the period (p<0.001). No significant difference was found between boys and girls. A significant increase in incidence was found in all age groups, with no disproportionate increase found in the 0 to 4-year-olds. Conclusions/interpretation. The incidence of childhood-onset Type 1 diabetes in Western Australia has increased significantly over the past 18 years and shows no signs of abating. In contrast to other studies, a higher rate of increase was not found in the youngest children.