TOPLINE:

The incidence of type 1 diabetes (T1D) in Sweden rose by 12% in 2021 and 9% in 2022 but reverted to pre-pandemic trends in 2023. The transient increase was particularly notable in children younger than 5 years and in young men and was only partially linked to SARS-CoV-2 infection.

METHODOLOGY:

• Previous studies have reported a rise in new T1D cases during the COVID pandemic, but whether this rise is linked to SARS-CoV-2 infections or other environmental and behavioral factors remains unclear.
• Researchers analyzed trends in T1D incidence in Sweden from 2007 to 2023 to identify changes during the pandemic years and assess the impact of SARS-CoV-2 infections, using the incidence in pre-pandemic years (2007-2019) as a reference.
• They included data from individuals younger than 30 years who lived in Sweden from 1990 to 2023 and considered three cohorts for analysis:
  • The individual infection cohort included those who tested positive for SARS-CoV-2 between February 2020 and 2022, with up to five matched control individuals.
  • The household infection cohort used the first SARS-CoV-2 infection in a household as a proxy for the infection date, focusing on younger age groups and including up to five matched control individuals.
  • A test-negative cohort was used for sensitivity analysis, matching individuals who tested positive with up to five control individuals who tested negative.
• Individuals with T1D were identified from three national registers and were considered vaccinated if they had received a second dose of the vaccine.
• The study included 727,605 individuals with confirmed SARS-CoV-2 infection and 3,535,503 matched control individuals in the individual infection cohort (nearly 51% female individuals) and 1,918,168 individuals with SARS-CoV-2 infection and 9,349,378 matched control individuals in the household infection cohort (nearly 49% female individuals).

TAKEAWAY:

• The incidence of T1D per 100,000 person-years was 35.6 in 2020, 41.1 in 2021, 40.5 in 2022, and 36.2 in 2023 compared with 33.1 in the pre-pandemic period. The incidence increased by 12% in 2021 and 9% in 2022 compared with pre-pandemic trends.
• Children aged 0-4 years experienced an increase in T1D incidence (2021-2022), with a 48% increase among boys (incidence rate ratio [IRR], 1.48; 95% CI, 1.20-1.81) and a 41% increase among girls (IRR, 1.41; 95% CI, 1.11-1.77) in 2022 vs the pre-pandemic period, with the rate reverting to pre-pandemic trends in 2023.
• Among young adults aged 18-29 years, the incidence increased significantly in men, primarily in 2021. No significant increase was noted in the overall risk of developing T1D.
• Children aged 5-10 years had a higher risk for T1D during the first 4 weeks post-infection (hazard ratio [HR], 2.68; 95% CI, 1.22-5.89) than those aged 18-29 years (HR, 0.82; 95% CI, 0.62-1.10). No associations were noted beyond 4 weeks of follow-up in any age group.

IN PRACTICE:

“Our findings suggest that the increases in type 1 diabetes incidence in Sweden during the pandemic can only partially be attributed to a potential triggering effect of SARS-CoV-2 infections. These findings suggest that, even with a relatively mild public health response to the pandemic, other behavioral and lifestyle risk factors for developing type 1 diabetes may have contributed to the increased incidence,” the authors of the study wrote.

“Infections do not seem to cause type 1 diabetes as such but may accelerate or trigger the onset among individuals who are already on the way to developing the disease,” the study author said in a press release.

SOURCE:

The study was led by Dominik Dietler, Division of Occupational and Environmental Medicine, Lund University, Lund, Sweden. It was published online in Diabetologia.

LIMITATIONS:

The testing rates among children were low, particularly for the youngest age groups. Misclassification of uninfected individuals as cases and control individuals as unexposed could bias the results toward the null. Selection bias may have occurred due to differences in testing behaviors.

DISCLOSURES:

The study was supported by grants from the Swedish Research Council, Sweden’s Innovation Agency, the Childhood Diabetes Foundation, and the Swedish Foundation for Strategic Research, along with open-access funding by Lund University. The research was also financed by Riksbankens Jubileumsfond. The authors declared having no conflicts of interest.

This article was created using several editorial tools, including AI, as part of the process. Human editors reviewed this content before publication.