A new cohort study has found that people who have had COVID-19 are at an increased risk of developing Type 2 diabetes.

As described in a  in the peer-reviewed medical journal Diabetologia, researchers at the German Centre for Diabetes Research and the German Diabetes Centre looked at the data of 8.8 million patients from 1,171 primary care physicians in Germany between March 2020 and January 2021. Follow-up continued until July 2021, according to the study.

"The aim of our study was to investigate the incidence of diabetes after infection with SARS-CoV-2," said first author and epidemiologist Wolfgang Rathmann in a press release.

During the study period, 35,865 individuals among the cohort were diagnosed with COVID-19. These individuals mostly had mild symptoms, and were treated in primary care settings rather than being hospitalized.

Another 35,865 individuals were selected to be a part of a control group made up of people with non-COVID-19-related acute upper respiratory tract infections (AURI), affecting the sinuses and throat. Patients in the COVID-19 group were compared against individuals in the AURI group based on their age, sex, time of diagnoses and comorbidities.

The researchers found that patients with COVID-19 developed Type 2 diabetes more frequently compared to those in the AURI group. For those with COVID-19, the incidence rate of Type 2 diabetes was 15.8 out of 1,000 people per year. In the AURI group, the incidence of diabetes was only 12.3 per 1,000 people per year.

"Put simply, this means that the relative risk of developing Type 2 diabetes was 28 per cent higher in the COVID-19 group than in the AURI group," Rathmann said in the release.

Researchers say the human pancreas is a target of SARS-CoV-2, the virus that causes COVID-19. Because of this, an infection could damage beta cells in the pancreas and impair the secretion of insulin. Cases of new-onset hyperglycaemia and insulin resistance have been reported in COVID-19 patients with no prior history of diabetes, the authors said.

However, the researchers say it's still not clear whether diabetes becomes apparent during COVID-19 infection due to immune activation or stress. It's also unclear whether post-COVID-19 diabetes may be reversed after a full recovery from infection.

The researchers suggest anyone who has or had COVID-19 should be on the lookout for warning signs and possible symptoms of diabetes, such as fatigue, frequent urination and increased thirst.

This is not the first study to investigate at a possible link between diabetes and COVID-19. A published in January found that diabetes was substantially more common in kids who had COVID-19. However, the report didn't distinguish between Type 1, which typically starts in childhood, and Type 2, the kind tied to obesity.

With files from The Associated Press.