Trends and Cyclic Variation in the Incidence of Childhood Type 1 Diabetes in Two Italian Regions Over 33 Years and During The Covid-19 Pandemic

Aims: There is conflicting evidence about the impact of the COVID-19 pandemic on the incidence of type 1 diabetes. Here we analyzed long-term trends in the incidence of type 1 diabetes in Italian children and adolescents from 1989 to 2019 and compared the incidence observed during the COVID-19 pandemic with that estimated from long-term data. Materials and methods: This was a population-based incidence study using longitudinal data from two diabetes registries in mainland Italy. Trends in the incidence of type 1 diabetes from 1 January 1989 through 31 December 2019 were estimated using Poisson and segmented regression models. Results: There was a significant increasing trend in the incidence of type 1 diabetes of 3.7% per year (95%CI 2.4-4.9) between 1989 and 2003, a breakpoint in 2003, and then a constant incidence until 2019 (0.5%, 95%CI -0.01-2.4). There was a significant four-year cycle in incidence over the entire study period. The rate observed in 2021 (26.7, 95%CI 23.0-30.9) was significantly higher than expected (19.5, 95%CI 17.6-21.4; p = 0.010). Conclusion: Long-term incidence analysis showed an unexpected increase in new cases of type 1 diabetes in 2021. The incidence of type 1 diabetes now needs continuous monitoring using population registries to better understand the impact of COVID-19 on new-onset type 1 diabetes in children. This article is protected by copyright. All rights reserved.