Background  
 Pre-existing diabetes in COVID-19 patients is considered an important and independent factor in the clinical severity of the infection, impacting the duration of hospital stay and prognosis. Furthermore, infected patients typically have altered glucose metabolism, which is reflected in higher daily insulin needs or newly-onset diabetes. 

Aim  
To identify the correlation between the insulin needs in COVID-19 patients and hospital stay and other related medical conditions. To identify the factors that would contribute to diabetes onset during COVID-19 infection.

Method  
 This is a retrospective cohort study analysing data from 96 COVID patients hospitalized between December 2020-March 2021. The cohort was stratified in 3 groups: patients already diagnosed with diabetes, patients with newly-onset diabetes, patients with no diabetes. Maximum total daily doses of Insulin (TDD) for each patient, based on glycemic profile, was calculated. Baseline characteristics, comorbidities and clinical prognosis, including hospital stay were also examined.

Results  
The participants age ranged from 28 to 84 years old (mean 62.6 years old). 64.6% of them (62/96 patients) had comorbidities prior to hospitalisation, with a predominance of cardiovascular diseases, mostly hypertension (51%). TDD varied from 0-132 UI/day (mean 19.4 UI/day, SD ±35.3). Only 26/96 patients were previously diagnosed with diabetes (17 on oral hypoglycemics and 9 on insulin), with a mean HbA1c 8.3 %. Patients with higher Insulin requirement had longer hospital stay (p 0.03) and compared to those with no diabetes, significantly more coexisting cardiovascular disease (p 0.01), including hypertension (p.0.02). 

In the group with unknown diabetes, 41/70 developed newly onset diabetes, with maximum TDD ranging from 12 to 130 UI/day (mean 55 UI/day, SD ±26.8). Higher HbA1c values in the day of admission were statistically correlated with longer hospital stay (p 0.01). Patients with newly-onset diabetes had significantly more coexisting cardiovascular disease (53.6% vs 24.1%, p 0.012) including hypertension (53.6% vs 24.1%, p 0.012). Also, we noticed longer hospital stay (p 0.07) using independent samples test.

Discussion  
Within the limits of our small cohort study, there are several points of interest. High insulin requirement determine hospital stay in diabetic patients, in correlation with cardiovascular comorbidities. The development of newly-onset diabetes is an area that needs further exploration. We pointed out that the patients with borderline HbA1c and related medical conditions are more predisposed to develop newly onset diabetes. It remains to be determined whether insulin requirement is due to insulin resistance as part of the systemic inflammation and critical illness or as a result of direct pancreatic beta-cell damage.

References  
Wu, L., et al. (2020). COVID‐19 and diabetes: insulin requirements parallel illness severity in critically unwell patients. Clinical Endocrinology, 93(4), 390-393.   
Lim, S., et al. COVID-19 and diabetes mellitus: from pathophysiology to clinical management. Nature Reviews Endocrinology, 17(1), 11-30.   
Verity, R., et al. (2020). Estimates of the severity of coronavirus disease 2019: a model-based analysis. The Lancet infectious diseases, 20(6), 669-677.   
Holman, N., Ket al. (2020). Risk factors for COVID-19-related mortality in people with type 1 and type 2 diabetes in England: a population-based cohort study. The lancet Diabetes &amp; endocrinology, 8(10), 823-833.



Diabetes Mellitus in hospitalized COVID-19 patients- a retrospective cohort study