Children who have had a Covid-19 infection are more likely to develop diabetes, particularly type 1 diabetes, in the month after infection, compared to children who haven’t had Covid, according to new research from the Centers for Disease Control and Prevention. The study was observational, so it cannot show that Covid causes diabetes. But it provides evidence of an increased diabetes risk that researchers need to examine more closely and try to understand better, especially since the findings revealed no increased risk of diabetes with other respiratory virus infections besides SARS-CoV-2. 

Previous research has shown that people with obesity or any type of diabetes have an increased risk of severe disease from Covid in both children and adults. But during the pandemic, clinicians have also observed an increase in type 1 diabetes diagnoses and more severe diabetic ketoacidosis at the time of diagnosis. Several studies have also identified increased diabetes diagnoses among adults during the pandemic.

Somewhat early in the pandemic, a systematic review and meta-analysis from November 2020 analyzed eight observational studies looking at new diagnoses of diabetes in people who had been hospitalized for Covid. It found that 14% of hospitalized Covid patients received a new diagnosis of diabetes. It’s certainly possible that some of these patients already had diabetes that hadn’t been identified before admission for Covid, but that’s not likely to explain all the cases. 

Then, a preprint—a study that has not yet been peer-reviewed—in January 2021 identified an increased risk of diabetes following a SARS-CoV-2 infection. This one also found higher rates of heart failure, acute kidney injury, ischemic stroke, heart attack, deep vein thrombosis, and pulmonary embolism. Since most of these are associated with acute infection, these events occurred after Covid patients’ discharge from the hospital. 

Since then, even more robust studies have identified similar trends. For example, a March 2021 study compared 47,780 Covid survivors discharged from the hospital with a control group of adults who hadn’t had Covid and were matched to the Covid patients. The study examined Covid patients and those without Covid based on age, sex, ethnicity, geographic region, socioeconomic factors, body mass index (BMI), smoking status, and underlying health conditions that included respiratory disease, cardiovascular disease, diabetes, chronic kidney disease, chronic liver disease, hypertension, and cancer. 

Just under a third (29%) of the Covid patients were readmitted to the hospital after discharge, and 12% died after discharge. The Covid patients received a new diagnosis of diabetes 1.5 times more often than those who hadn’t had Covid. Covid patients were also three times more likely than those without Covid to have heart failure, a heart attack, stroke, or arrhythmia after discharge. Covid patients were 2.8 times more likely to be diagnosed with new chronic liver disease and 1.9 times more likely to have new chronic kidney disease than those without Covid. 

As the link between Covid and the new onset of diabetes has become more evident, researchers have sought out possible mechanisms to explain the association. A study in Cell Metabolism in August 2021 conducted experiments to determine whether SARS-CoV-2 impacted the pancreas, where insulin is produced. Indeed, the researchers found that the novel coronavirus affects insulin levels and can directly cause cell death in beta cells, which has already been linked to increased insulin resistance. 

In the same issue of Cell Metabolism, a separate study investigated pancreatic beta cells in autopsy samples from patients who had died from Covid. The researchers found SARS-CoV-2 antigens—the part of the virus that the immune system recognizes as foreign—in beta cells. In addition, these beta cells expressed lower amounts of insulin, further supporting the possibility that a SARS-CoV-2 infection can instigate the process contributing to diabetes. 

An even more recent study in Cell Metabolism, published in November 2021, found that half of all Covid patients had hyperglycemia, and 91% of all Covid patients who were intubated had hyperglycemia. As with any observational study, the challenge is figuring out what’s the chicken and the egg. Researchers already know that people with diabetes have an increased risk of severe Covid, hospitalization, and death. What’s unclear is whether the association cuts both ways: Is SARS-CoV-2 contributing to insulin resistance even in people who did not have diabetes when they developed the infection? 

And that brings us back to the newest study investigating this phenomenon in children who have had Covid. The researchers examined healthcare claims for Covid patients under 18 in two healthcare databases, one from March 2020 through February 2021 and the other from March 2020 through June 2021. For both data sets, one with 80,893 patients and the other with 439,439 patients, the average patient age was 12. These patients were then matched to individuals with similar demographics who did not have Covid. 

Hospitalization rates were low in both groups, 0.7% and 0.9% in the other, matching the low hospitalization risk among children and teens with Covid. In the first database, children with Covid were 2.6 times more likely to receive a new diagnosis of diabetes more than a month after their SARS-CoV-2 infection than their peers without Covid. In the other database, Covid patients were 1.3 times more likely to develop new diabetes a month after infection than those without Covid. As with the other studies looking at new cases of diabetes, some of these may have been cases that existed but were not identified before they got sick with Covid, but it’s unlikely to account for all the cases. 

The researchers did not control their analysis for body mass index (BMI), which is strongly associated with type 2 diabetes. However, obesity is not associated with type 1 diabetes, and type 2 diabetes is half as likely to occur in children under ten years old as type 1 is. Still, the new study has several limitations that make it too early to conclude that a SARS-CoV-2 infection can lead to diabetes in patients under 18. Instead, the findings suggest it’s essential for clinicians to watch for this possibility and perhaps mention it to families asking about vaccination as one more reason pediatric Covid vaccination is wise.