During the pandemic, the incidence of type 1 diabetes (T1D) increased, but the jump could not be attributed to COVID-19 in a 2015–2021 study of all residents of Denmark who did not initially have diabetes and were younger than 30 years.
Study participants were followed from Jan. 1, 2015, or birth, until the development of T1D, the age of 30, the end of the study (Dec. 31, 2021), emigration, development of type 2 diabetes, the onset of any cancer, initiation of immunomodulating therapy, or development of any autoimmune disease. The incidence rate ratio (IRR) of T1D using Poisson regression models showed these patterns for each person with a SARS-CoV-2 infection and 3 control individuals: “Among 2,381,348 individuals, 3,579 cases of T1D occurred. The adjusted IRRs for T1D in each quarter of 2020 and 2021 compared with 2015–2019 were as follows: January–March 2020, 1.03 (95% CI 0.86; 1.23); January–March 2021, 1.01 (0.84; 1.22), April–June 2020, 0.98 (0.80; 1.20); April–June 2021, 1.34 (1.12; 1.61); July–September 2020, 1.13 (0.94; 1.35); July–September 2021, 1.21 (1.01; 1.45); October–December 2020, 1.09 (0.91; 1.31); and October–December 2021, 1.18 (0.99; 1.41). We identified 338,670 individuals with a positive SARS-CoV-2 test result and matched them with 1,004,688 control individuals. A SARS-2-CoV infection was not significantly associated with the risk of T1D development (HR 0.90 [95% CI 0.60; 1.35]).”