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08-03-2022 | Diabetes | News | Article

Threshold effect for HbA1c association with poor COVID-19 outcomes

Author: Eleanor McDermid

medwireNews: Researchers confirm that higher glycated hemoglobin (HbA1c) levels are associated with a higher risk for poor outcomes in people with type 2 diabetes and COVID-19, but the risk does not increase further beyond a certain threshold.

Specifically, the risk for death within 30 days plateaued at HbA1c higher than 8% (64 mmol/mol) and that for invasive ventilation or extracorporeal membrane oxygenation (ECMO) above 9% (75 mmol/mol).

This threshold effect “does not reflect the traditional dose-dependent exposure risk of glycemia established in the literature for long-term microvascular complications,” write the researchers in Diabetes Care.

For the study, Rachel Wong (Stony Brook University, New York, USA) and team used data from the US National COVID Cohort Collaborative (N3C), identifying 39,616 people with type 2 diabetes who were diagnosed with COVID-19 across 35 sites.

This makes it “the largest multicenter U.S. cohort study of HbA1c and COVID-19 outcomes to date,” they say.

The study participants were an average age of 62.1 years and 50.9% were women. More than half (55.4%) were White, with 26.4% being Black or African–American, and 16.1% Hispanic or Latino.

In all, 5.7% of participants died within 30 days of their COVID-19 diagnosis, which was the researchers’ primary endpoint.

Mortality risk was increased by a significant 1.17-fold for people with an HbA1c of 7% to less than 8% (53 to <64 mmol/mol), relative to those with an HbA1c of 6% to less than 7% (42 to <53 mmol/mol), and by a significant 1.40-fold for those with an HbA1c of 8% up to 9% (64 to 75 mmol/mol).

But the risk did not increase further with higher HbA1c levels, at 1.37- and 1.46-fold for people with levels of 9% to less than 10% (75 to <86 mmol/mol) or of 10% or higher.

There was a similar pattern for the risk for invasive ventilation or ECMO, which occurred in 7% of the cohort. The risk increase for this outcome was 1.24-fold for HbA1c levels of 7% to less than 8% (compared with 6% to <7%) and 1.59-fold for levels of 9% to less than 10%, but did not increase further with higher HbA1c.

By contrast, the risk for hospitalization rose with higher HbA1c level, with no sign of a threshold effect.

People with a BMI of 40 kg/m2 or higher were at significantly increased risk for all the above outcomes, as were people with a BMI below 20 kg/m2, which the researchers say “may be reflective of a frailer population with poor nutritional status.”

In line with previous studies, taking a non-insulin diabetes medication was associated with a significantly reduced risk for most outcomes. The exceptions were dipeptidyl peptidase-4 inhibitors for mortality and thiazolidinediones for all outcomes, although there were nonsignificant trends toward a reduced risk. Use of insulin – potentially a marker for longer/more advanced type 2 diabetes – was linked to a higher risk for poor outcomes.

medwireNews is an independent medical news service provided by Springer Healthcare Ltd. © 2022 Springer Healthcare Ltd, part of the Springer Nature Group

8 March 2022: The coronavirus pandemic is affecting all healthcare professionals across the globe. Medicine Matters’ focus, in this difficult time, is the dissemination of the latest data to support you in your research and clinical practice, based on the scientific literature. We will update the information we provide on the site, as the data are published. However, please refer to your own professional and governmental guidelines for the latest guidance in your own country.

Diabetes Care 2022; doi:10.2337/dc21-2186

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