Fourteen percent of patients who experience a severe case of Covid-19 have developed new-onset diabetes, according to a new analysis—a troubling trend without clear cause or explanation, according to experts.

A growing problem

According to the Washington Post's Erin Blakemore, Covid-19, while primarily a respiratory illness, has been linked to an array of health issues, including blood clots, heart damage, neurological disorders—and now, potentially, new-onset Type 1 and Type 2 diabetes.

According to Blakemore, physicians in China noticed high blood sugar levels among Covid-19 patients as early as January 2020, and doctors in Italy expressed concern that diabetes diagnoses could follow.

To examine that risk, researchers conducted a global analysis that was published late last year in Diabetes, Obesity and Metabolism. The researchers examined reports of high blood sugar, or uncontrolled hyperglycemia, among more than 3,700 Covid-19 patients, and they found that up to 14.4% of patients hospitalized with Covid-19 developed diabetes.

But even now, researchers are unsure whether that link means that Covid-19 actually causes diabetes.

Blakemore explains that many Covid-19 patients who develop diabetes have other risk factors for the condition, including a family history of diabetes. Further, high sugar levels are common among patients taking the steroid dexamethasone, a front-line treatment for Covid-19.

However, physicians also have diagnosed new diabetes cases among Covid-19 patients who didn't have any risk factors—and even among Covid-19 patients who had been free of the virus for several months.

In their analysis, the researchers acknowledged these complicating factors but said the possibility that new-onset diabetes was a direct result of Covid-19 "should also be considered." In fact, the researchers said this possibility is supported by the experiences of Covid-19 patients with pre-existing cases of diabetes, who often need very high doses of insulin while ill and experience dangerous complications.

Researchers navigate a host of unknowns

Much remains unknown about the correlation between Covid-19 and diabetes, Blakemore writes, but researchers "are racing" to learn more.

For instance, researchers are studying whether and how the novel coronavirus might interact with beta cells, which are involved in both Type 1 and Type 2 diabetes. According to Blakemore, there's evidence that ACE2 receptor cells, which are the novel coronavirus' "entryway into the body," are on beta cells—a finding that appears to support the idea that viruses can trigger diabetes, although the research remains inconclusive.

"If scientists could figure out how or if viral infection can damage beta cells, or what role viruses play in the development of the disease, it would be a real turning point," Katie Colbert Coate, a diabetes researcher and research instructor of medicine at Vanderbilt University Medical Center, said.

According to researchers, it's also unclear whether these new diabetes diagnoses are permanent or temporary. After the 2003 SARS outbreak—which was also correlated with new-onset diabetes—researchers in China monitored 39 patients who, despite having no previous history of the disorder, developed acute diabetes within days of being hospitalized with SARS. Among those patients, all but six experienced a decrease in their blood sugar levels by the time they were discharged, and just two still had diabetes two years later.

Researchers are also exploring whether all Covid-19-related diabetes diagnoses even fit into the familiar Type 1 or Type 2 categories. According to Francesco Rubino, a diabetes surgery professor at King's College London, some of the more than 150 cases filed in his global registry of patients who've experienced Covid-19 related diabetes do not fit the profile of either Type 1 or Type 2 diabetes. These patients appear to experience symptoms and complications that span both diagnoses.

"There's a good chance that the mechanism of the diabetes isn't typical," he said. "There could be a hybrid form. It's concerning."

Rubino also cited concerning reports of diabetes diagnoses among patients with asymptomatic or relatively mild cases of Covid-19, noting that as the virus spreads, "you could see a significant new volume of diabetes diagnoses." That's particularly worrisome, Blakemore writes, given how prevalent diabetes already is in the United States, with an estimated 34.5 million Americans believed to have the condition and another 88 million more believed to have prediabetes, which can—if not addressed—lead to a Type 2 diagnosis.

"We really need to dig deeper," Rubino added. "But it sounds like we do have a real problem with [C]ovid and diabetes" (Blakemore, Washington Post, 2/1).