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COVID-19 and diabetes can interact at multiple levels. We know that in patients with existing diabetes the risk of developing COVID-19 is higher, as is the risk of a more severe illness. Also, similar to other viral infections, diabetes may be more difficult to control and require medication changes during an acute COVID-19 infection.
MBBS, MAACB, FRCPA
Lab: Clayton Speciality: Chemical Pathology
Areas Of Interest: Endocrine Function Testing, Protein Abnormalities, Laboratory Automation
Several recent studies have also shown that some people can also develop type 2 diabetes after COVID-19 infection.
Study One
One such study is from Germany and was published in 2022.1 The subjects were from a primary care setting who mostly had mild COVID-19 disease.
The incidence of new diabetes was compared with a control group who had non-COVID-19 acute upper respiratory tract infections. The two groups were matched on a range of factors including sex, age, health insurance coverage, month of disease and comorbidity factors including obesity, hypertension, hyperlipidaemia, myocardial infarction and stroke. Patients with a prior history of diabetes or steroid use were excluded. Each group had a total of almost 36,000 participants.
The COVID-19 group had a 28% higher rate of developing type 2 diabetes compared with the control group. (15.8 vs 12.3 per 1000 person-years). There was no increased rate for other forms of diabetes.
Study Two
This study is from the US and utilised the databases of the US Department of Veterans Affairs for patient data.
Researchers also compared post-acute phase COVID-19 patients (181,000) with a control group who had not contracted SARS-CoV-2 (4.1 million), as well as a historical control group (4.3 million) from a pre-pandemic era. All members of these groups were free of diabetes before the study and were followed up for a median of 352 days.
Measures of incident diabetes and anti-hyperglycaemic use, and a composite of the two outcomes were used to assess the development of diabetes post COVID-19. They reported the results as a hazard ratio and burden per 1000 people at 12 months.
People with COVID-19 exhibited an increased risk (40% higher) than the control group and excess burden (13.46 per 1000 people) of incident diabetes. This was also seen in antihyperglycaemic use with an increased risk (85% higher) than the control group and excess burden (12.35 per 1000 people).
The composite endpoint gave an increased risk (46% higher) than the control group and an excess burden of 18.03 per 1000 people at 12 months. The hazard ratios and burdens increased according to the severity of the acute phase of COVID-19 (whether patients were non-hospitalised, hospitalised or admitted to intensive care).
All the results were consistent in analyses using the historical control as well as the reference category. These are just two of several studies that have shown the link between diabetes and COVID-19. Most of the studies associate COVID-19 with type 2 diabetes and a Scottish study found no increase in type 1 diabetes post COVID-19.3
Why can diabetes present after COVID-19?
There are several possible mechanisms by which COVID-19 could increase the incidence of type 2 diabetes. One is by altering the metabolic and hormonal status of post COVID-19 patients which results in higher blood glucose levels and diabetes, especially in people who are predisposed to the condition.
It is also possible that the virus may affect the beta cells of the pancreatic islets and cause disruption of normal insulin production and release. The virus could also result in cross-reacting antibodies which could affect the beta cells.
Other factors which also should be considered include any drugs, such as steroids, that may have been used by COVID-19 infected patients, as well as the diet, weight and exercise level of people post COVID-19. We also should not discount the effect of post COVID-19 patients having more medical contact which may increase the pick-up rate of diabetes.
Discussion
As the COVID-19 patients in the above studies were only followed for a relatively short time, further follow-up is needed to determine if the diabetes is just temporary and may resolve or whether it becomes a chronic condition.
Although type 2 diabetes is not likely to be a problem for the vast majority of people who have mild COVID-19 and there are no specific guidelines yet to screen post COVID-19 patients for diabetes, it may be wise to have a high index of suspicion and check for diabetes if there are any features suggestive of diabetes in post COVID-19 patients, especially if they already have risk factors or pre-diabetes.
References on request
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