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.