Diabetes mellitus and the risk of post-acute COVID-19 hospitalizations: a nationwide cohort study

Aims: This cohort study, based on Danish health registers, examined the post-acute consequences of hospitalization for COVID-19 in patients with diabetes. Methods: The study population comprised all Danish citizens (≥18 years old) who had diabetes when the pandemic started. A patient was exposed if he/she had a hospitalization with COVID-19 after 1 March 2020. A patient was unexposed when he/she was not hospitalized with COVID-19 between 1 March 2020 and the end of follow-up (4 January 2022), or the first registered event of interest. The outcomes included post-COVID-19 hospitalizations and death. We used a Cox proportional hazards model with time varying exposure estimating the hazards ratio (HR) to analyze if the hazard for an outcome of interest was impacted by being hospitalized with COVID-19. Results: In patients with type 1 diabetes, 101 were hospitalized with COVID-19, and 25,459 were not. We did not have sufficient statistical power to identify differences in risk for those with type 1 diabetes. In type 2 diabetes, 1515 were hospitalized with COVID-19, and 95,887 were not. The adjusted HRs of post-acute hospitalization for respiratory diseases and infections were 1.71 (95% CI 1.45–2.03) and 1.87 (95% CI 1.61–2.18), respectively. The HR of death was 2.05 (95% CI 1.73–2.43). Patients with uncertain type had results similar to those with type 2 diabetes. Conclusions/Interpretation: In type 2 diabetes and diabetes of uncertain type, hospitalization with COVID-19 was associated with an increased risk of post-acute hospitalization for respiratory diseases, infections and death.