Background: Diabetes mellitus (DM) confers a two-fold increased risk of death from COVID-19 and overall poorer prognosis compared to the general population. Metformin is a widely used first-line antidiabetic agent with anti-inflammatory and immunomodulatory effects. Several studies report reduced COVID-19-related mortality in patients with DM on metformin. Few studies have corroborated these findings within a multiracial, multiethnic population.

Methods: This was a retrospective cohort study of patients with DM admitted with COVID-19 to 1 of 3 urban academic hospitals from 1/1/20 to 5/7/20. We compared in-hospital mortality and length of stay (LOS) in COVID-19 patients with diabetes on metformin compared to those not on metformin. Patient demographic and clinical characteristics were summarized and compared between both groups. Logistic regression and linear regression analysis were applied to study the association between metformin treatment and in-hospital mortality and LOS, respectively.

Results: A total of 4462 patients were identified. Overall, 46.9% were female, with a mean age of 64.4 years; 41.3% were Black and 41.5% Hispanic. There were 1021 in the metformin group and 3441 in the non-metformin group. The prevalence of hypertension (58.2% vs.37.5%, P<.0001) and coronary artery disease (13.4% vs. 6.7%, P<0.0001) was higher in the metformin group compared to the non-metformin group. BMI (30.5 vs. 29.4) , HbA1c (8.2 vs. 6.5) creatinine (1.6 vs. 2.1) , and mean number of antidiabetic agents (1.2 vs. 0.22) were also significantly higher in the metformin group. The odds of death (OR 1.0, 95% CI 0.8-1.3; p=0.900) and mean LOS (p= 0.486) were not significantly different in the metformin vs. non-metformin group, after adjusting for confounding variables.

Conclusion: There was no significant difference in in-hospital mortality and LOS in the metformin vs. non-metformin group. The metformin group had a significantly higher comorbidity burden, as well as higher BMI, mean HbA1c, and creatinine. Further prospective studies are needed.


E. Miao: None. K. Zhang: None. J. Liu: None. J. Lin: None. C. George: None.

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