COVID-19 is notorious for sometimes leaving an aftermath of聽puzzling symptoms, such as fatigue or concentration difficulties. But doctors are also worried about the coronavirus triggering a more familiar condition: diabetes.
In countries that are dropping coronavirus precautions, it seems likely that nearly everyone will get infected at some point. So what do聽we know so far about the link between the virus and diabetes聽鈥� and how will health services cope?
Diabetes is an umbrella term for聽several conditions that involve high blood sugar, and can lead to serious complications, such as heart attacks. The body normally keeps blood sugar within a narrow window, as too high a level can damage organs and blood vessels.
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The main hormone that brings down blood sugar into a safe range after meals is insulin. Nine in 10 people with diabetes have a form called type聽2, which is usually seen in聽people who are overweight and is聽linked with cells becoming resistant to insulin. A less common form, called type聽1, usually arises in聽childhood, and聽is聽caused by the聽death of pancreas cells that make聽insulin.
The strange thing with covid-19 is that doctors are seeing a rise in both kinds of diabetes after infections. Signs of a rise were noticed in in Wuhan, China,聽and have since been confirmed in other countries.
Most of the studies on this link so聽far have been descriptive ones, looking at people who go to聽hospital for covid-19 and are diagnosed with diabetes while there. More recently, researchers have begun estimating how often diabetes arises after the infection, including in people who didn鈥檛 go to hospital, who account for聽most covid-19 cases.
, for instance, estimated that anyone with a positive covid-19 test聽has about a 40聽per cent higher chance of developing any kind of聽diabetes in the following year, compared with uninfected people. found an increased risk for type聽2 diabetes of聽28聽per cent over about four months. The picture for type聽1 diabetes is less clear as some specialist clinics have , but not all have.
There are several possible explanations for the pattern. Firstly, about 1聽per cent of people in the UK are thought to have undiagnosed type聽2 diabetes. If such people go to聽hospital because of covid-19 and聽their blood sugar is聽tested, the聽condition will be revealed, says Anna Morris at charity Diabetes UK.
Alternatively, many kinds of illness, including other viral infections, stress the body in various ways and so cause blood sugar levels to rise, a聽phenomenon called stress hypoglycaemia. 鈥淚f聽someone鈥檚 unwell, you get production of lots of聽hormones that raise glucose levels,鈥� says at Norfolk and Norwich University Hospitals NHS聽Foundation Trust, UK.
Once the illness resolves, the symptoms may abate, so in theory the diabetes diagnosis is only temporary, although those affected are at a higher risk of developing true聽type 2 diabetes later in life.
It is similar to the way that diabetes sometimes temporarily develops during pregnancy and then resolves after birth, although people聽are still at higher risk after,聽says Dhatariya.
Another possible mechanism is聽that the coronavirus could be directly infecting the cells in the pancreas that make insulin and harming or killing them. Some studies have shown that these cells聽have the ACE2 receptor that the聽virus uses to enter cells. Or the pancreas cells could be harmed by the raised level of inflammation caused by the immune system鈥檚 response to the virus.
More than one of these explanations could be contributing to聽the apparent rise聽in new diabetes cases, says at Leicester General Hospital in the UK.
Confusing matters further, there have been some reports of people with signs of both type聽1 and type 2 diabetes after a covid-19 infection. These include people who already had type 2 diabetes, but covid-19 seemed to trigger a聽syndrome called ketoacidosis, usually a hallmark of type聽1 diabetes, says at聽King鈥檚 College London.
Rubino鈥檚 group has begun a聽 of people with diabetes related to the virus to try to聽understand the mechanisms involved and their prognosis. 鈥淲e聽need to understand which [cases] could have occurred anyway and which were triggered by the virus,鈥� he says.
Diabetes healthcare services were聽already under pressure, with cases rising thanks to more people being overweight and individuals becoming more overweight. Any surge caused by the pandemic will only worsen problems, says at VA St Louis Health Care System in Missouri, who was involved in the US study. 鈥淓ven if only 1 or 2聽per cent of people with covid develop it, the sheer colossal scale of聽the pandemic will mean millions of people will聽have new diabetes.鈥�
Al-Aly warns anyone who has had the infection to watch out for diabetes symptoms, such as thirst, fatigue and a frequent need to urinate. 鈥淧eople need to be on the look-out,鈥� he says.
