How does coronary vasodilator dysfunction affect the prognosis of type 1 diabetes mellitus (DM), and how does diabetes affect mortality in coronavirus disease 2019 (COVID-19)?

Updated: Dec 01, 2020
  • Author: Romesh Khardori, MD, PhD, FACP; Chief Editor: George T Griffing, MD  more...
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In both diabetic and non-diabetic patients, coronary vasodilator dysfunction is a strong independent predictor of cardiac mortality. In diabetic patients without coronary artery disease, those with impaired coronary flow reserve have event rates similar to those with prior coronary artery disease, while patients with preserved coronary flow reserve have event rates similar to non-diabetic patients. [47]

A study by Bode et al indicated that among patients with coronavirus disease 2019 (COVID-19), the US in-hospital death rate for individuals living with diabetes, patients with an HbA1c of 6.5% or higher, and those with hyperglycemia throughout their stay is 29%, a figure over four times greater than that for patients without diabetes or hyperglycemia. Moreover, the in-hospital death rate for patients with no evidence of preadmission diabetes who develop hyperglycemia while admitted was found to be seven times higher (42%). [48, 49]

A whole-population study from the United Kingdom (UK) reported that the risk of in-hospital death for patients with COVID-19 was 2.0 times greater for those with type 2 diabetes and 3.5 times higher for individuals with type 1 diabetes. However, patients under age 40 years with either type of diabetes were at extremely low risk for death. [50, 51]

Another study, by Barrera et al, looking at 65 observational reports (15,794 participants), found that among COVID-19 patients with diabetes, the unadjusted relative risk for admission to an intensive care unit (ICU) was 1.96, and for mortality, 2.78. [52, 53]

Another study from the UK found that risk factors for mortality in COVID-19 patients with type 1 or type 2 diabetes include male sex, older age, renal impairment, non-White ethnicity, socioeconomic deprivation, and previous stroke and heart failure. Moreover, patients with type 1 or type 2 diabetes had a significantly greater mortality risk with an HbA1c level of 86 mmol/mol or above, compared with persons with an HbA1c level of 48-53 mmol/mol. In addition, an HbA1c of 59 mmol/mol or higher in patients with type 2 diabetes increased the risk as well. The study also found that in both types of diabetes, body mass index (BMI) had a U-shaped relationship with death, the mortality risk being increased in lower BMI and higher BMI but being reduced between these (25.0-29.9 kg/m2). [54, 51]

However, a Belgian study, by Vangoitsenhoven et al, indicated that in most people, the presence of type 1 diabetes mellitus is not associated with a greater risk of hospitalization for COVID-19. The investigators found that during the first 3 months of the pandemic in Belgium, the COVID-19 hospitalization rate was similar between individuals with type 1 diabetes and those without (0.21% vs 0.17%, respectively). Among the patients with type 1 diabetes, older persons had a greater tendency toward COVID-19–related hospitalization, although glucose control, comorbidity profile, and angiotensin-converting enzyme (ACE) inhibitor/angiotensin II receptor blocker (ARB) therapy did not significantly differ between the hospitalized and non-hospitalized groups. This and other research suggest that in persons with type 1 diabetes, an increased risk of death from COVID-19 is found primarily in particularly vulnerable individuals instead of in such patients overall. [55, 56]

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