At 18 months into the COVID-19 pandemic, many of the direct and indirect effects of SARS-CoV-2 on people with diabetes have become clearer, but knowledge gaps remain, say epidemiologists.
“COVID-19 has had a devastating effect on the population with diabetes, and conversely, the high prevalence of diabetes and uncontrolled diabetes has exacerbated the problem,” Edward W. Gregg, PhD, Imperial College London, lead author of a new literature review, told this news organization.
“As it becomes clear that the COVID-19 pandemic will be with us in different forms for the foreseeable future, the emphasis for people with diabetes needs to be continued primary care, glycemic management, and vaccination to reduce the long-term impact of COVID-19 in this population,” he added.
In data, mostly from case series, the review shows that more than one-third of people hospitalized with COVID-19 have diabetes. It is published in the September issue of Diabetes Care.
People with diabetes are more than three times as likely to be hospitalized for COVID-19 than those without diabetes, even after adjustment for age, sex, and other underlying conditions. Diabetes also accounts for 30%-40% of severe COVID-19 cases and deaths. Among those with diabetes hospitalized for COVID-19, 21%-43% require intensive care, and the case fatality rate is about 25%.
In one of the few multivariate analyses that examined type 1 and type 2 diabetes separately, conducted in the U.K., the odds of in-hospital COVID-19–related deaths, compared with people without diabetes, were almost three times higher (odds ratio, 2.9) for individuals with type 1 diabetes and almost twice as high (OR, 1.8) for those with type 2, after adjustment for comorbidities.
The causes of death appear to be a combination of factors specific to the SARS-CoV-2 infection and to diabetes-related factors, Dr. Gregg said in an interview.
“Much of the increased risk is due to the fact that people with diabetes have more comorbid factors, but there are many other mechanisms that appear to further increase risk, including the inflammatory and immune responses of people with diabetes, and hyperglycemia appears to have an exacerbating effect by itself.”
Elevated glucose is clear risk factor for COVID-19 severity
Elevated A1c was identified among several other overall predictors of poor COVID-19 outcomes, including obesity as well as comorbid kidney and cardiovascular disease.
High blood glucose levels at the time of admission in people with previously diagnosed or undiagnosed diabetes emerged as a clear predictor of worse outcomes. For example, among 605 people hospitalized with COVID-19 in China, those with fasting plasma glucose 6.1-6.9 mmol/L (110-125 mg/dL) and ≥7 mmol/L (126 mg/dL) had odds ratios of poor outcomes within 28 days of 2.6 and 4.0 compared with FPG <6.1 mmol/L (110 mg/dL).
Population-based studies in the U.K. found that A1c levels measured months before COVID-19 hospitalization were associated with risk for intensive care unit admission and/or death, particularly among those with type 1 diabetes. Overall, the death rate was 36% higher for those with A1c of 9%-9.9% versus 6.5%-7%.
Despite the link between high A1c and death, there is as yet no clear evidence that normalizing blood glucose levels minimizes COVID-19 severity, Dr. Gregg said.
“There are data that suggest poor glycemic control is associated with higher risk of poor outcomes. This is indirect evidence that managing blood sugar will help, but more direct evidence is needed.”