Relation of incident type 1 diabetes to recent COVID-19 infection: cohort study using e-health record linkage in Scotland

Objective – Studies using claims databases reported that SARS-CoV-2 infection >30 days earlier increased the incidence of type 1 diabetes. Using exact dates of diabetes diagnosis from the national register in Scotland linked to virology laboratory data we sought to replicate this finding. 

Research Design and Methods – A cohort of 1,849,411 individuals aged <35 years without diabetes, including all those in Scotland who subsequently tested positive for SARS-CoV-2, was followed from 1 March 2020 to 22 November 2021. Incident type 1 diabetes was ascertained from the national registry. Using Cox regression we tested the association of time-updated infection with incident diabetes. Trends in incidence of type 1 diabetes in the population from 2015-2021 were also estimated in a generalised additive model. 

Results – There were 365,080 individuals who had at least one detected SARS-CoV-2 infection during follow-up and 1074 who developed type 1 diabetes. The rate ratio for incident type 1 diabetes associated with first positive test for SARS-CoV-2 (reference category: no previous infection) was 0.86 (95% CI 0.62 to 1.21) for infection > 30 days earlier and 2.62 (95% CI 1.81 to 3.78) for infection in the previous 30 days. However negative and positive SARS-CoV-2 tests were more frequent in the days surrounding diabetes presentation. In those aged 0-14 years incidence of type 1 diabetes during 2020-2021 was 20% higher than the 7-year average. 

Conclusions – Type 1 diabetes incidence in children increased during the pandemic. However the cohort analysis suggests that SARS-CoV-2 infection itself was not the cause of this increase.