Studies link Covid-19 infection with increased risk of new diabetes diagnosis

By Tasnim Ahmed, CNN

Over a year after recovering from a Covid-19 infection, Jennifer Hobbs is adjusting to her new normal: brain fog, joint pain, elevated liver enzymes and, now, type 2 diabetes. Hobbs had prediabetes before she got Covid-19, but her blood sugar levels were under control, and she didn’t need any treatment. Recently, that changed.

“I take my blood sugar [level] every morning, and even with two different types of medication, it’s all over the place,” said Hobbs, 36. The new diabetes diagnosis has both Hobbs and her primary care provider wondering if the coronavirus has played a role.

Two years into the pandemic, scientists and physicians are shifting their attention to the long-term consequences of a Covid-19 infection, termed “long Covid.” Recent studies add diabetes to the list of possible long Covid outcomes.

Experts have known that people with diabetes are at higher risk of severe Covid-19 infection, but now, a new connection is unraveling — one in which a Covid-19 infection may lead to a higher risk for diabetes.

One study published this month looked at people who had mild Covid-19 infections in Germany and found that they were 28% more likely to have a new diagnosis of type 2 diabetes compared with people who were never infected.

A study in the United States similarly found an increased incidence rate of diabetes in people who had recovered from Covid-19: a 40% increase in risk at least a year after infection. The researchers estimate that about 2 out of every 100 people who are infected with Covid-19 will have a new diagnosis of diabetes.

This US-based study, published last week in the medical journal The Lancet, also found that even among people who had low to no risk factors for diabetes, Covid-19 infection led to a 38% increased risk of diabetes afterward.

The more severe someone’s coronavirus infection was, the higher their risk of diabetes. For people who were treated in the ICU, the risk of diabetes jumped 276%. This connection could be related to the steroids that some patients get while receiving acute care in a hospital setting, which can increase blood sugar levels.

“This is not diabetes for a month or two after recovery. This is for a year out, and it’s happening certainly in people who are not hospitalized,” said lead researcher Dr. Ziyad Al-Aly, chief of research and development at the VA St. Louis Health Care System and a clinical epidemiologist at Washington University in St. Louis.

That study used the national databases for the US Department of Veterans Affairs to follow over 180,000 people after they got Covid-19. The research team compared this group’s outcomes to outcomes for a control group of over 4 million people from before the pandemic, along with another group of over 4 million people during the pandemic who did not get Covid-19.

In kids, the overall risk of newly diagnosed diabetes is even worse. A report from the US Centers for Disease Control and Prevention published in January found that children were over 2½ times as likely to be diagnosed with diabetes after a Covid-19 infection than those who were never infected over a month after infection.

Investigating the link

For many years, theories have circulated about inflammation from viral infections being implicated with diabetes. However, according to Dr. Robert Gabbay, chief scientific and medical officer at the American Diabetes Association, this is the first time studies have shown such a stark relationship between diabetes and a specific virus.

It’s still not clear to scientists why Covid-19 is placing people at risk for diabetes. One theory involves the receptor where the virus attaches in the lungs, which is also present in the pancreas.

“There’s been a number of studies that do show that SARS-CoV-2 can attack the beta cells of the pancreas and may cause at least temporary harm, if not more permanent harm,” said Dr. Sara Cromer, an assistant in medicine at Mass General Hospital in the Division of Endocrinology, Diabetes, and Metabolism. She was not involved in the two new studies.

Beta cells are pancreatic cells that produce insulin. As these cells are destroyed by Covid-19 infection, the body may lose its ability to make insulin. This is similar to what happens in type 1 diabetes, an autoimmune disorder in which the body destroys its own beta cells and therefore cannot make insulin.

“It’s also possible that there’s the acute inflammation of getting Covid which may be present in low levels, even in asymptomatic or minimally symptomatic cases,” Cromer said. “That can lead to a short-term insulin resistance, which can maybe snowball or set off a chain of events that leads to more longer-term insulin resistance.”

This second theory would better explain the development of type 2 diabetes, the most common form, in which the body is still making insulin but grows resistant to it and thus cannot respond to it. Type 2 diabetics made up more than 99% of the newly diagnosed diabetes cases after Covid-19 infection that Al-Aly’s study identified.

Cromer said other factors could contribute to this increased risk for diabetes.

“When you’re diagnosed with SARS-CoV-2, you might stay at home a little while, you might eat differently, you might not exercise. There’s a number of ways that it might affect your lifestyle and behavior, and we don’t really know how those might interact with metabolic disease, either,” she said.

In a study led by Cromer, her research team found that people with newly diagnosed diabetes after Covid-19 tended to be younger, Black or Hispanic, and underinsured.

“We thought that a number of these people might have had pre-existing diabetes that had not been diagnosed because they had poor access to health care,” Cromer said.

Eleven months after her Covid-19 infection, Claudia Mendez, 45, was diagnosed with type 2 diabetes during an urgent care visit. Her blood glucose level was found to be 300, a marked increase from the normal level of below 140. For Mendez, studies like these are finally answering the questions that Covid long-haulers have had for the past two years.

“It’s a double-edged sword just because you never want to be in this place, but to hear that it’s even being acknowledged is, in a sense, a relief,” she said.

These studies do not imply that specific diabetes cases like those of Mendez and Hobbs were directly caused by the coronavirus, but they’re changing the way doctors think about the relationship between the two conditions.

Now, Covid-19 may need to be considered a risk factor for diabetes. “I think the big message for clinicians is … that knowing that somebody had Covid infection should raise your awareness about potentially screening them for diabetes,” Gabbay said.

Care for chronic conditions

As diabetes is added to the emerging list of post-Covid complications, experts are worried about the staggering impact it will have on an already strained health care system.

“Inevitably, this is going to create a large number of people with newly diagnosed diabetes,” Al-Aly said. “This has really serious downstream ramifications and would require care for a lifetime. … I think we need to be prepared to really build the capacity to deal with these patients.”

The question remains whether America’s health care system is ready to handle the spike in chronic conditions emerging from the pandemic. Al-Aly’s research team recently also found that people with Covid-19 infections had a 60% increase in cardiovascular disorders after recovery.

“We already are challenged to care for all of the people with diabetes that currently exist. The last thing we need is increasing the numbers,” Gabbay said.

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