Evidence of a plateau in the incidence of type 1 diabetes in children 0-4 years of age from a regional pediatric diabetes center; Auckland, New Zealand: 1977-2019

Objective: To determine the incidence of new onset type 1 diabetes in children aged 0-14 years from 1977 to 2019 in Auckland, New Zealand.

Research design and methods: A cohort study of children with type 1 diabetes aged 0-14 years (n = 1688; 50.4% male) managed by the regional diabetes service between 1977 and 2019. Incidence rates were estimated using census data.

Results: The incidence of type 1 diabetes increased by 2.9%/year from 1977 to 2006 (95% confidence interval [CI] 2.13% - 3.48%). Although there was no significant change from 2006 to 2019 (-0.3%/year, 95% CI -1.62% - 1.08%), there was a dramatic fall from 1976 to 2018 in the proportion of New Zealand Europeans, from 69.9 to 33.9%. New Zealand Europeans had the highest incidence (23.3/100,000, 95% CI 20.6-26.1) compared to Māori (8.3/100,000, 95% CI 6.3-10.2), Pasifika (8.6/100,000, 95% CI 6.9-10.4) and other (6.4/100,000, 95% CI 4.7-8.0). All groups showed an overall increase in incidence over time, Māori 4.4%/year, Pasifika 3.7%, compared to New Zealand European 2.7%, and other 2.1%. Incidence increased consistently in 5-9 and 10-14 year olds (2.0% and 2.2%/year, respectively). By contrast, whereas 0-4 year olds showed an increase of 4.6%/year from 1977 to 2003 (p < 0.01), there was no change from 2003 to 2019 (p = 0.2).

Conclusion: There has been a plateau in the incidence of type 1 diabetes in children 0-4 years of age in the Auckland region since 2003, but not older children. The apparent plateau in the overall incidence of new onset type 1 diabetes in children 0-14 years since 2006 was mediated by substantial changes in the ethnic makeup of the Auckland region.