Increasing incidence of type 1 diabetes in children and adolescents from 2012 to 2021 in Germany: trends before and during the COVID-19 pandemic

Type 1 Diabetes (T1D) is a common chronic autoimmune disorder in children and adolescents worldwide. We described the development of T1D incidence from 2012 to 2021 and compared the incidence of the pre-pandemic period (2012-2019) with the pandemic period (2020-2021) in Bavaria, Germany. Routinely collected health claims from the Bavarian Association of Statutory Health Insurance Physicians (KVB), covering a population of 2 million children and adolescents (aged ≤ 19 years), were used. All cases of newly diagnosed T1D (ICD-10-GM E10) were included. Sex-specific annual and quarterly crude incidence rates (CIR) and age-standardized incidence rates (ASIR) were calculated. Sex-specific CIRs were calculated by 5-year age groups. Interrupted time series analysis was used to analyze trend changes in the pandemic versus the pre-pandemic period. From 2012 to 2021, 5,762 incident cases were identified in Bavaria. Overall, an increasing incidence was observed with an average annual increase of 3.7% in females (from 23.5 in 2012 to 32.5 per 100,000 person-years (py) in 2021) and 5.0% in males (from 25.2 to 38.9 per 100,000 py). The increase was highest in age groups 0-4 (12.4%) in males and 15-19 (8.5%) in females. Regression analysis showed no clear level or slope change in T1D incidence for both sexes during the pandemic period. When accounting for non-linear trends, a statistically significant level change was observed for females during the pandemic period (ß=7.66, 95% CI 0.23, 15.09), suggesting a potential association for females. The increasing T1D incidence in Bavarian youth from 2012 to 2021 highlights the importance of incidence surveillance.