Impact of COVID-19 outbreak on the seasonality and incidence of type 1 diabetes mellitus: A nationwide cohort study.

BACKGROUND

Type 1 diabetes mellitus (T1DM) is an autoimmune disease with a multifactorial pathogenesis. Viral infections have been proposed as contributing triggers, supported by the disease's seasonal pattern, which typically shows higher incidence in autumn and winter. The coronavirus disease 2019 (COVID-19) pandemic and associated lockdowns created a unique context to examine the incidence and seasonality of T1DM during a period characterized by reduced circulation of common viral infections.

AIM: To investigate the incidence and seasonality of T1DM before and during COVID-19 pandemic in relation to global viral infection rates.

METHODS

This population-based retrospective study utilized a nationwide computerized database. Extracted data included the number of new T1DM cases over the 8 years preceding and during the COVID-19 pandemic, demographic characteristics of affected individuals, and nationwide respiratory virus polymerase chain reaction data from weekly nasal wash sample collections.

RESULTS

A total of 2176 patients were diagnosed with new-onset T1DM during the pre-pandemic period, compared to 348 cases during the pandemic. In the same periods, 33727 respiratory virus-positive polymerase chain reaction results from nasal wash samples were recorded pre-pandemic, compared to 2603 during the pandemic. Additionally, 363399 positive COVID-19 cases were reported during the pandemic period. Seasonality analysis revealed a higher rate of new-onset T1DM cases and a weaker seasonal pattern during the pandemic. Trend analysis showed a consistent increase in T1DM incidence prior to COVID-19, with a more variable trend observed during the pandemic. Correlation analysis between T1DM incidence and respiratory viruses demonstrated a weak correlation between T1DM incidence and a few respiratory viruses.

CONCLUSION

The observed increase in new-onset T1DM cases and the disruption of its typical seasonal pattern during the COVID-19 pandemic suggest a potential association between respiratory virus exposure and the development of T1DM.