Risk of New-Onset Diabetes Following COVID-19 Infection: A Systematic Review of Cohort Studies

Abstract

Background: Emerging evidence suggests a link between SARS-CoV-2 infection and increased incidence of new-onset diabetes in adults. Diabetes affects over 537 million adults globally, with cases projected to reach 783 million by 2045, highlighting its growing public health burden. This systematic review aimed to determine whether adults infected with COVID-19 are at increased risk of developing new-onset diabetes compared to matched uninfected controls, by synthesising findings from retrospective cohort studies and assessing their methodological quality. Methods: A comprehensive search of MEDLINE (Ovid), PubMed, Scopus, and Cochrane CENTRAL identified eight matched cohort studies conducted in the UK and US between 2020 and 2024. All studies compared adults with confirmed COVID- 19 to uninfected controls; three included other viral infections. Diabetes outcomes were defined using ICD-10 codes alone or combined with HbA1c (≥6.5%), fasting glucose, or prescription data. Risk of bias was assessed using the Newcastle–Ottawa Scale. Results: All studies reported a statistically significant increase in diabetes risk following COVID-19. Risk was highest among unvaccinated, obese, prediabetic, or severely ill individuals. Studies using laboratory data showed stronger associations than those relying only on diagnosis codes. One study found 60% of new cases persisted beyond four months. Some evidence suggested a lower risk of diabetes in vaccinated individuals, with an 8.8-fold increase observed in the unvaccinated compared to 1.6-fold in the vaccinated. Conclusion: COVID-19 is associated with an increased risk of new-onset diabetes. Future research should adopt standardised diagnostics, extend follow-up, explore biological mechanisms, and include diverse populations. Findings also support the broader protective role of vaccination.