COVID, Then a Diabetes Diagnosis

New research finds that COVID-19 can bring on diabetes in patients who were not prediabetic before infection

With Sathish Thirunavukkarasu PhD, MBBS, MPH and Elena Christofides, MD, FACE

COVID-19 can lead to diabetesMany patients who were not prediabetic are developing diabetes after COVID-19.

Soon after COVID-19 was declared a pandemic in March 2020, researchers reported that having diabetes increases the risk of having a severe case of COVID and a bad outcome. More recently, however, researchers have found an opposite link: That a new diagnosis of diabetes is often found in people diagnosed with COVID-19.

So, having diabetes worsens the outlook if you get COVID, and contracting COVID now appears to increase the chance you will get a diagnosis of diabetes.

In a recent study, researchers found that 14.4% of 3,711 patients diagnosed with COVID also learned they had diabetes.

"These findings suggest that COVID19 could be a diabetogenic (diabetes-producing) virus," said study researcher Sathish Thirunavukkarasu PhD, MBBS, MPH, an investigator and post-doctoral fellow at the Population Health Research Institute at McMaster University in Hamilton, Ontario, Canada.

Study Details

Dr. Thirunavukkarasu and his team looked to the medical literature, searching several databases to find already published studies that looked at how many COVID-19 patients had newly diagnosed diabetes. They found 148 studies and after excluding duplicate studies, commentaries, case reports and other studies that did not meet their criteria, boiled down that number to eight that met their standards. They conducted a meta-analysis, an approach in which researchers analyze previously published studies. The studies were done in the US, Italy and China.

The studies had definite limitations, Dr. Thirunavukkarasu told Endocrine Web.  Only one study reported on the type of diabetes, whether type 1 or type 2, for instance. He is assuming most of the cases were type 2. The blood sugar measurement known as HbA1c, which looks back at blood sugar levels over the previous 2-3 months, was not done on all the study participants, making it impossible to differentiate between new-onset diabetes and that which had simply gone undetected. Information on the exact time of the diagnosis was not always reported, but in two of the studies, it was made within 24 hours to 3 days after the patient was admitted.

Another unknown is that researchers cannot yet say if the new diagnosis of diabetes in COVID patients is transient and goes away once the COViD-19 patient recovers, Dr. Thirunavukkarasu said.

In a more recent study, the researchers have found limited evidence also suggesting people with prediabetes—blood sugar levels that are above normal but not high enough to be termed diabetes—are also at risk of poorer outcomes if they get COVID-19. "It's not as strong a link as in those with diabetes," Dr. Thirunavukkarasu said.

Explaining the Link

What might explain COVID-19 leading to a new diagnosis of diabetes? According to Dr. Thirunavukkarasu, that is still under study. While the stress that understandably accompanies severe illness might explain it, the ''diabetogenic effect"—that is, that the COVID somehow triggers the diabetes—needs to be considered.

Some research has found that the virus that causes COVID can attached to receptors in the insulin-producing cells in the pancreas and lead to impaired secretion of the insulin. Thirunavukkarasu said the virus may also injure beta cells by triggering inflammation or enhancing autoimmunity—the body turning against itself—at least in people who are genetically predisposed to autoimmune diseases. (Autoimmune disorders include Graves' disease, multiple sclerosis and Addison's disease.)

Expert Perspective

Elena Christofides MD, FACE, an endocrinologist in Columbus, OH, reviewed the study. "Viral infections are known triggers to autoimmune disease and this is well established for type 1 diabetes," she said, noting that although people consider type 1 diabetes a condition limited to the pediatric population, it is also diagnosed in adults.  "I think what is happening with COVID is simply that it is making people more aware and the identification of the diabetes is more acute," meaning the diabetes develops faster than it normally does.

The take-home advice for anyone who gets COVID, Dr. Christofides said, is that they should be aware that this is more likely to happen in those with a family history of autoimmune disease in general, but not necessarily diabetes. 

The new research, she said, may inspire people to take precautions to prevent COVID more seriously if they think it might lead to diabetes. As to another question, whether a COVID vaccine will protect you, ''there is no way to answer that at this time. What we can say is that the vaccine can protect you from getting severe COVID and the more severe the infection, the more likely that an autoimmune disease can be triggered."

Until more is known, Dr. Christofides suggested: "Anyone who has obesity or been told that they are at risk for diabetes should be aware that a COVID diagnosis can worsen their metabolic health and lead to a new diagnosis of diabetes, type 1 or type 2."

The Researcher's Take-Away

The research is suggesting that if you get infected with COVID, the increased possibility that you will develop diabetes, at least for the short-term, exists. So staying as healthy as possible might help people avoid a severe case. "We don't know if it persists," he said of the diabetes diagnosis. "We need longer term data to find out if the diabetes is transient."

For those who have diabetes already, ''they should have their blood sugar under control, because we know from a large number of studies that an increase in blood sugar leads to poor outcome from COVID-19 if you should get infected" more than diabetes itself.

Soon, more information should be available. As the research has accumulated about the COVID-diabetes link, Dr. Thirunavukkarasu said, ''More and more hospitals and clinics are doing more and more blood sugar testing for those admitted with COVID."

A registry to study the link further has been established, Dr. Thirunavukkarasu said. "So far, about 350 institutions have signed up." He advises doctors that COVID patients with newly diagnosed diabetes should be followed closely to manage their diabetes and keep their blood sugar stable. He called the link "a classic example of a lethal intersection between a communicable and a non-communicable disease."

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