New cases of diabetes
At the start of the coronavirus pandemic, doctors started to raise concerns around new cases of diabetes in people who had caught the virus.
Since early reports first came to light, we’ve seen results from larger studies looking at big groups of people who’ve recovered from coronavirus. One study tracked over 47,000 people in England who had been admitted to hospital because of coronavirus before August 2020. The researchers followed their health for up to seven months after they were discharged and found 5% of people went on to develop diabetes.
They also showed that people who’d been in hospital with coronavirus were 1.5 times more likely to be diagnosed with diabetes after they’d been discharged than people of the same age and background who hadn’t been in hospital with coronavirus.
In 2022, researchers in the United States published findings from their analysis of health insurance data from around 1.6 million children, under the age of 18 years.
They looked at who’d been diagnosed with diabetes between March 2020 – March 2021 and if there were any differences in rates of diagnoses between children who’d had coronavirus, children who hadn’t, and children who had other types of respiratory infections. The study didn’t distinguish between type 1 and type 2 diabetes.
The researchers studied two different sets of data. In both datasets, children who’d had coronavirus were more likely to later be diagnosed with diabetes than those who hadn’t had coronavirus or had a different type of respiratory infection.
In the first dataset, the researchers found after having coronavirus, children were around 2.5 times (166%) more likely to develop diabetes than children who hadn’t been infected. In the other dataset the increased risk was smaller, at 31%. These differences in risk are likely down to differences in the way data was classified and collected. Respiratory infections that weren’t coronavirus were not found to be linked with an increased risk of diabetes.
The evidence to suggest a link between coronavirus and new cases of diabetes is growing but there’s still a lot we don’t know. We can’t yet be sure if coronavirus is directly causing diabetes, or whether there are other factors that could explain the link.
What type of diabetes?
Small studies have suggested that rates of new type 1 diabetes diagnoses in children were higher in 2020 compared to average rates in previous years.
The causes of type 1 diabetes are complex, and scientists think that there are a variety of environmental and genetic reasons that could explain why the condition develops.
Viruses could be one of these reasons, but the evidence around this is mixed and we just don’t know for sure yet. And as coronavirus is so new, there’s a lot we still need to learn about how it interacts with our immune system and its longer-term effects.
Cases of new type 2 diabetes diagnoses have also been reported in people who have had coronavirus. This could be related to the effects of coronavirus on the body, or the effects of lifestyle changes due to the pandemic, speeding up a type 2 diabetes diagnosis or bringing existing type 2 to light.
Scientists are also looking into the possibility that coronavirus could be causing a new type of diabetes. Blood sugar levels in some people with coronavirus rise due to the stress the body is under when trying to fight the infection, or because of some of the drugs used to treat it. But we don’t yet know if, or when, high blood sugar levels in people with coronavirus return to normal after they have fully recovered.
What’s going on inside the body?
One theory is that inflammation inside the body caused by coronavirus brings about insulin resistance, a feature of type 2 diabetes, which means the body isn’t able to make proper use of the insulin it’s producing.
We also know that coronavirus uses a protein found on the surface of some cells, called ACE-2, to enter and infect them. ACE-2 is found in the pancreas and there’s some evidence that this makes it vulnerable to coronavirus infection.
Small studies looking at pancreas cells grown in the lab and pancreas samples taken from people who sadly died from coronavirus have suggested that the virus can enter and infect insulin-producing beta cells in the pancreas, causing them to die or change how they work. This means people can’t produce enough insulin.
Another theory suggests that when coronavirus infects the pancreas it could trigger the immune system to attack and destroy beta cells, a key feature of type 1 diabetes.
Research into the biological processes that explain how and why coronavirus could cause diabetes is at an early stage and we need to be cautious about applying what scientists see in the lab to what’s happening in people infected with the virus. And we need more research to look at the types of diabetes we’re seeing in people who have had coronavirus to understand whether these are cases of type 1 and type 2 diabetes or something new altogether.
Scientists are working hard to find answers and are building a database of new cases of diabetes in people with coronavirus, called the CoviDiab registry. This will give them the information they need to carry out more thorough studies and discover more.
On top of this, the government has pledged £18.5 million to fund research to better understand and treat the longer term effects of coronavirus. These projects could give us important insights into new cases of diabetes after coronavirus.
Research, including the PHOSP-COVID study, will also help us to fully understand if coronavirus can make existing type 2 diabetes worse in people who already live the condition. The UK-wide study is following 10,000 people who were in hospital with coronavirus to monitor the long-term impact of the virus on their health. This study will include people with type 2 diabetes and will help us to understand how their condition has been affected.