Association of COVID-19 and Development of Type 1 Diabetes - A Danish Nationwide register study
Objective: To compare the incidence of type 1 diabetes (T1D) before and during the COVID-19 pandemic and if SARS-CoV-2 is associated with T1D development.
Research Design and Methods: All Danish residents under 30 years free of diabetes from 2015 to 2021 were included. Individuals were followed from 01.01.2015 or birth until the development of T1D, the age of 30, the end of the study (31.12.21), emigration, development of type 2 diabetes, onset of any cancer, initiation of immune modulating therapy, or development of any autoimmune disease. We compared the incidence rate ratio (IRR) of T1D using Poisson regression models. We matched each case with a SARS-CoV-2 infection with three controls and used a cause-specific Cox-regression model to estimate the hazard ratio.
Results: Among 2,381,348 individuals, 3,579 cases of T1D occurred. The adjusted IRRs [95% confidence interval] for T1D in each quarter of the year in 2020 and 2021 compared to 2015-2019 were: Jan-Mar-2020: 1.03 [0.86;1.23], Jan-Mar-2021: 1.01 [0.84;1.22], Apr-Jun-2020: 0.98 [0.80;1.20], Apr-Jun-2021: 1.34 [1.12; 1.61], Jul-Sep-2020: 1.13 [0.94;1.35], Jul-Sep-2021: 1.21 [1.01;1.45], Oct-Dec-2020: 1.09 [0.91; 1.31], Oct-Dec-2021: 1.18 [0.99; 1.41]. We identified 338,670 individuals with a positive SARS-CoV-2 test and matched them with 1,004,688 controls. A SARS-2-CoV infection was not significantly associated with the risk of T1D development (Hazard rate ratio of 0.90 [0.60-1.35]).
Conclusions: There was an increase in T1D incidence during Apr-Jun 2021 compared to Apr-Jun 2015-2019, but this could not be attributed to the SARS-CoV-2 infection.