Importance: Diabetes has been reported to be associated with an increased risk of death among patients with COVID-19. However, available studies lack detail on COVID illness severity and measurement of relevant comorbidities. Design, Setting, and Participants: We conducted a multicenter, retrospective cohort study of patients over the age of 18 years who were hospitalized with COVID-19 between January 1, 2020 and November 30, 2020 in Ontario, Canada and Copenhagen, Denmark. Chart abstraction emphasizing co-morbidities and disease severity was performed by trained research personnel. The association between diabetes and death was measured using Poissson regression. Main Outcomes and Measures: within hospital 30-day risk of death. Results: Our study included 1018 hospitalized patients with COVID-19 in Ontario and 305 in Denmark, of whom 405 and 75 patients respectively had pre-existing diabetes. In both Ontario and Denmark, patients with diabetes were more likely to be older, have chronic kidney disease, cardiovascular disease, higher troponin levels, and to receive antibiotics compared with adults who did not have diabetes. In Ontario, the crude mortality rate ratio among patients with diabetes was 1.60 [1.24 — 2.07 95% CI] and in the adjusted regression model was 1.20 [0.86 — 1.66 95% CI]. In Denmark, the crude mortality rate ratio among patients with diabetes was 1.27 (0.68 — 2.36 95% CI) and in the adjusted model was 0.90 (0.49 — 1.54 95% CI)]. Meta-analyzing the two rate ratios from each region resulted in a crude mortality rate ratio of 1.55 (95% CI 1.22,1.96) and an adjusted mortality rate ratio of 1.11 (95% CI 0.84, 1.47). Conclusions: Presence of diabetes was not strongly associated with in-hospital COVID mortality independent of illness severity and other comorbidities.

The authors have declared no competing interest.

This research is supported by Sinai Health Department of Medicine Research fund.

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The REBs of Mount Sinai Hospital, Trillium Health Partners, Michael Garron Hospital, Southlake Regional Health Centre, University Health Network, The Ottawa Hospital Research Institute, Unity Health Toronto and University of Copenhagen gave ethical approval for this work.

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