The rising incidence of childhood type 1 diabetes in New South Wales, 1990-2002

OBJECTIVES: To determine the incidence of childhood type 1 diabetes mellitus (T1DM) in New South Wales from 1997 to 2002; to compare with previously published rates (1990-1996); and to analyse trends in incidence from 1990 to 2002. DESIGN, SETTING AND PARTICIPANTS: Prospective population-based incidence study. Primary ascertainment of incident cases aged < 15 years was from the Australasian Paediatric Endocrine Group NSW children's diabetes register. Secondary ascertainment was from the National Diabetes Supply Scheme until 1999 and from the Australian Institute of Health and Welfare thereafter. Childhood population data were obtained from the Australian Bureau of Statistics. MAIN OUTCOME MEASURES: Age-standardised incidence; trends in incidence by calendar year, and sex and age at diagnosis. RESULTS: There were 3260 incident cases (1629 boys, 1631 girls) in the 13 years. Case ascertainment was 99.7% complete using the capture-recapture method. Mean age-standardised incidence per 100 000 person-years was 20.9 (95% CI, 19.9 to 21.9) from 1997 to 2002 compared with 17.8 (95% CI, 17.0 to 18.7) from 1990 to 1996; there was a plateau in incidence between 1997 and 2002. Overall, the incidence increased on average by 2.8% per year (95% CI, 1.9% to 3.8%, P < 0.001) and increased with age, being 12.2 (95% CI, 11.3 to 13.1) in 0-4 year olds; 18.9 (95% CI, 17.8 to 20.0) in 5-9 year olds and 26.7 (95% CI, 25.4 to 28.1) in 10-14 year olds. The increase per year in 0-4 year olds (3.9%) was not significantly higher than in older children. The mean incidence of T1DM was 19.8 (95% CI, 18.8 to 20.7) in girls and 18.8 (95% CI, 17.9 to 19.7) in boys (P = 0.02). CONCLUSIONS: The incidence of childhood-onset T1DM has increased significantly in all age groups in NSW since 1990. Resource planning in the management of childhood diabetes in NSW should take these findings into account.