New Study Finds COVID Linked With Higher Risk For Type 2 Diabetes

Could COVID-19 infection leave people more likely to develop type 2 diabetes? A new study of more than 600,000 people in British Columbia linked COVID-19 to a higher risk of diabetes more than 30 days after diagnosis. An estimated 3 to 5 percent of diabetes cases may be attributable to COVID-19, according to the research published on April 18, 2023, in JAMA Network Open.

These findings suggest that healthcare organizations and medical professionals need to be mindful of the possible long-term outcomes of COVID-19, says lead author Naveed Janjua, MBBS, DrPH, an epidemiologist and clinical professor at the UBC School of Population and Public Health in Vancouver, British Columbia.

“Given these findings, it may be important to monitor individuals who have recovered from COVID-19 for diabetes, especially those who had more severe disease during acute phase of infection, as early detection and treatment can be critical in managing diabetes,” he says.

What Earlier Studies Say About the COVID-Diabetes Link

It's estimated that about 37 million people — 11.3 percent of the population — have diabetes in the United States, according to the latest data from the Centers for Disease Control and Prevention (CDC). About 1.4 million American adults are diagnosed each year.

Ongoing research suggests that COVID-19 may be associated with long-term health problems such as diabetes after the acute phase of illness, says Dr. Janjua.

Several studies have linked COVID-19 to diabetes, including one from The Lancet published in May 2022 that included over 180,000 subjects. Researchers found that people who survived COVID-19 had a 40 percent higher risk for developing diabetes.

But a Cleveland Clinic study published in December 2022 found no link between COVID-19 and diabetes. The authors concluded that many people with COVID-19 who ended up with a diabetes diagnosis had likely already had the condition but just didn’t know it until they sought out treatment for the virus.

Because many previous studies looking at the link had small or specific participant groups, the findings may not represent the general population, says Janjua. “We conducted this study using population-level data from the British Columbia COVID-19 Cohort to better understand the relationship between COVID-19 infection and the risk of developing diabetes,” he says.

Having COVID-19 Associated With a 17 Percent Increased Risk of Developing Diabetes

The study included nearly 630,000 people, including 125,987 people who had COVID-19. Participants who tested positive for COVID-19 were matched in a 1 to 4 ratio with those with negative test results. The median participant age was 32 years and 51.2 percent were women. The median follow-up was 257 days.

“We found that COVID-19 is associated with higher risk of diabetes following COVID-19 infection,” says Janjua.

There was a 17 percent higher risk of new-onset diabetes in the COVID group, and men had a 22 percent higher risk of developing T2D.

“The risk was higher among people who had severe COVID-19 disease during the acute phase of COVID-19 infection, such as among those who required hospitalization or admission to the intensive care unit,” says Janjua.

Being in an ICU due to COVID-19 more than tripled the risk for developing diabetes, and being hospitalized for the virus more than doubled the likelihood of T2D.

A total of 784 of the diabetes cases were classified as insulin-dependent, while 1,688 were typed as non-insulin-dependent. Further analysis revealed that COVID-19 was tied to the non-insulin-dependent type only, although the study authors said this finding could have been influenced by the relatively few insulin-dependent diabetes cases in the sample.

Investigators also looked at participants according to vaccination status, and the link between COVID-19 and diabetes was only found among unvaccinated participants.

According to the authors’ calculations, the proportion of COVID-attributable diabetes was 3.41 percent overall and 4.75 percent among men.

How Could COVID Infection Increase the Likelihood of Type 2 Diabetes?

Why COVID-19 could be increasing diabetes risk is not completely clear at this stage, says Janjua. “Some studies have suggested that SARS-CoV-2 could infect cells that produce insulin in the pancreas, leading to alteration of their function and insulin production,” he says.

It’s also been suggested that chronic low-grade inflammation, common in people with obesity, autonomic dysfunction, hyperactivated immune response or autoimmunity, could also play a role in diabetes, says Janjua.

Although this study on the connection between COVID-19 and diabetes is larger and more rigorous than some earlier studies, there still needs to be more research in order to show a definite link, says Yogish Kudva, MBBS, professor of medicine and endocrinologist at Mayo Clinic in Rochester, Minnesota.

“They observed that the risk of diabetes is increased in people who have developed COVID, and that risk is related to severity of illness and perhaps also to sex. This is not surprising,” says Dr. Kudva.

In this study, COVID-19 was linked to non-insulin-dependent diabetes, which is mostly a form of type 2 diabetes and is associated with lifestyle and physical fitness, he says. “People who are hospitalized or on a ventilator lose muscle mass, they lose physical fitness, and physical fitness alters glucose control [and] homeostasis,” says Kudva. It is possible that those factors, not necessarily COVID infection, are responsible for the increase in type 2 diabetes, he says.

Although it makes sense that some earlier studies were observational and retrospective, the next steps should be a prospective study with a comparison group, he says. “For example, following another group of people in the same season, perhaps with flu, who have the same level of hospitalization and ventilation and look at the risk of diabetes in each group,” says Kudva. A study like that would be able to tease out factors such as undiagnosed diabetes or diabetes caused by lack of fitness, versus diabetes caused by COVID, he says.

Rehab and Physical Activity May Help Reverse Type 2 Diabetes

Diet and physical activity may help in controlling diabetes risk, says Janjua.

Kudva agrees that lifestyle plays a big role and may even help reverse type 2 diabetes in many individuals who are diagnosed after having COVID-19. “People who have severe illness and require hospitalization and/or ventilation become deconditioned. Once they leave the hospital, they need to work on their physical fitness because that is likely to impact their health in months and years,” he says.

And finally, even though vaccination was not directly assessed in this study, being fully vaccinated could reduce diabetes risk through prevention of infection and severe disease, says Janjua.