Children who had Covid-19 may be at higher risk of developing type 1 diabetes than those who did not, a new study suggests.

The research, which looked at health records of more than one million children aged 18 and younger, found a 72% increase in new diagnoses of the condition in coronavirus patients.

However, the researchers highlight that it is not clear why type 1 diabetes appears to be more common after Covid, and experts say more research is needed.

Pamela Davis, Distinguished University Professor at the Case Western Reserve School of Medicine – a study corresponding author, said: “Type 1 diabetes is considered an autoimmune disease.

“It occurs mostly because the body’s immune defences attack the cells that produce insulin, thereby stopping insulin production and causing the disease.

“Covid has been suggested to increase autoimmune responses, and our present finding reinforces that suggestion.”

Jamie Hartmann-Boyce, Associate Professor at the Nuffield Department of Primary Care Health Sciences, University of Oxford, said: “The team uses a strong study design to investigate this link, comparing people with Sars-CoV-2 to a matched group with other respiratory viruses during the same period.

“However, there is still some uncertainty as to whether Covid-19 causes type 1 diabetes, or if something else links the two.

“Covid testing, particularly at the start of the pandemic, was not widespread in young people, and type 1 diabetes is also not regularly tested for, which makes it hard to establish if one could cause the other.

He added: “More studies like that presented here need to be done to see if the same results are found using different methods and in different groups of people.”

Gareth Nye, Programme Lead for Medical Science & Lecturer in Physiology at University of Chester, said: “There are many factors to appreciate in this finding and this study does not attempt to prove mechanistic links between the two simply observational ones and so we should take the results with careful consideration.

“We may for example be seeing undiagnosed type 1 diabetes being brought to light due to the additional infection or simply that following an infection they are more likely to be more closely monitored. ”

He added: “It certainly is worth reminding the public to be on the lookout for four ‘T’ symptoms of type 1 diabetes for an early diagnosis and prompt treatment: needing the toilet more, being thirstier, becoming thinner and more tired as this will undoubtedly save lives.”

Researchers analysed the health records of nearly 1.1 million patients in America and 13 other countries diagnosed with Covid between March 2020 and December 2021 and also those diagnosed with a non-Covid respiratory infection.

Patients were further divided into two groups – those up to nine years old and those aged 10-18 years.

The study found that among more than 571,000 patients aged under 18, within six months of Covid infection, 123 patients (0.043%) had received a new diagnosis of type 1 diabetes, compared to 72 patients (0.025%) who received a new diagnosis following a non-Covid respiratory infection, an increase of 72% in new diagnoses.

Researchers found that one, three and six months after infection, the risk of diagnosis of type 1 diabetes was substantially higher for those infected with Covid compared to those with non-Covid respiratory infections.

Similar results were reported with patients in the infant to nine-year-old and 10 to 18-year-old age groups.

Prof Davis said: “Families with high risk of type 1 diabetes in their children should be especially alert for symptoms of diabetes following Covid, and paediatricians should be alert for an influx of new cases of type 1 diabetes, especially since the Omicron variant of Covid spreads so rapidly among children.

“We may see a substantial increase in this disease in the coming months to years.

“Type 1 diabetes is a lifelong challenge for those who have it, and increased incidence represents substantial numbers of children afflicted.”

The findings are published in the journal Jama Network Open.

Dr Faye Riley, research communications manager at Diabetes UK, said: “Research worldwide has identified higher than expected numbers of new onset type 1 diabetes in people who have had Covid-19, but there are still question marks surrounding how they are linked, and whether other factors are at play.

“While these findings add to evidence of a possible link between Covid-19 and type 1 diabetes, it is still unclear whether Covid-19 could directly increase your risk of developing type 1 diabetes.”