New research finds high blood sugar levels to correlate with COVID-19 mortality, even in people with no history of diabetes. The findings suggest the need for early blood glucose screenings in people with SARS-CoV-2 infections.

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Who is at risk of dying from COVID-19? Ongoing research has identified vulnerable populations — including people with immunocompromised states, people aged 65 years or older, and people with underlying health conditions. Yet it is still unclear why COVID-19 can also be deadly for people who are not in high-risk groups.

Because excess sugar in the blood is linked to type 2 diabetes, a major risk factor for severe COVID-19 and death, a team of researchers in Spain has investigated whether high blood sugar levels alone correlate with COVID-19-related mortality.

The results of their study appear in the journal Annals of Medicine.

The researchers used a national registry to analyze data from 11,312 COVID-19 positive patients in 109 hospitals in Spain from March 1 to May 31, 2020. Patients were excluded from the study if they made repeated hospital visits or did not provide informed consent.

Registry information included, but was not limited to, treatments, laboratory test results, and symptoms. The average patient age was 67.06 years, and 57.1% were male.

The researchers considered the patients to have diabetes if there was a record of the diagnosis or evidence of diabetes medication use before hospital admission. Only 18.9% of patients in the study had diagnosed diabetes.

Blood sugar levels were taken upon hospital admission, and the team used this information to categorize the patients into three groups: normal, high, and very high blood sugar.

The researchers found that high blood sugar levels were associated with older men with a history of diabetes, hypertension, or another health condition. The team also observed elevated levels of inflammation markers more frequently in patients with high blood sugar levels.

One of the most prominent findings was that as blood sugar levels increased, the risk of death from COVID-19 also rose. This association was not affected by a history of diabetes.

Of the 11,312 patients included in the study, 2,289 — or 20.2% — died of COVID-19. Among this group, 41.1% had very high blood sugar levels, while 15.7% had normal levels.

Patients with very high blood sugar levels were admitted to hospitals for slightly longer than those with normal levels. They also required more intensive care unit attendance and more invasive or noninvasive ventilation.

The first limitation involves the study design — this was an observational, retrospective cohort study. The researchers reviewed the patients’ hospitalization records to study how specific symptoms and other characteristics affected their outcomes. Unlike in an experiment, the researchers could not measure or control for outside variables.

The authors also acknowledged that a majority of inflammatory markers were not included in the registry. This is important because several correlate with the severity of COVID-19 illness.

Recently, a study in Nature Medicinefound inflammatory markers such as elevated serum interleukin 6, interleukin 8, and tumor necrosis factor-alpha levels were strong predictors of COVID-19 survival.

In addition, some patients did not know their diabetes status because they did not have their average blood glucose level measurements. This leaves the possibility of skewed results, as patients who had diabetes may have been mistakenly assigned to a nondiabetes group.

Despite several shortcomings, however, the authors highlight the importance of their study — most COVID-19 studies focus on severely ill patients, leaving limited data about others who are not in a critical condition.

“On the other hand, as a strength, our registry is the largest available cohorts of non-critically ill, hospitalized patients with confirmed COVID-19. […] It includes data from over 11,000 patients on admission [and their blood glucose] levels before starting any treatment,” the researchers emphasize.

Improving mortality rates may require refining COVID-19 protocols to include blood glucose screenings upon hospital admittance.

“Early glycemic control may be a suitable therapeutic option to reduce the poor outcomes in hospitalized, hyperglycemic COVID-19 patients with or without a previous diabetes diagnosis,” write the study authors.

Blood glucose screenings upon hospital admission may be essential for prioritizing treatment for patients at high risk of death from COVID-19.

This early intervention would be especially helpful for racial and ethnic groups with a predisposition for type 2 diabetes and who have been disproportionally affected by the COVID-19 pandemic.

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