This Sunday, we bring to you an old article from Dr. V Mohan's exclusive series, in which he answers one of the most pertinent questions regarding the continuing pandemic- whether COVID-19 has an effect on chronic diseases, specifically diabetes.

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For our comprehensive coverage and latest updates on COVID-19 click here.

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The raging COVID-19 pandemic produces multiple effects on the body. The complications involving the upper and lower respiratory tract are well recognised, with fever, cough, and breathlessness being common. A cluster of 6 symptoms have recently been described based on the severity of the COVID infection. 

• 'Flu-like’ with no fever: Headache, loss of smell, muscle pains, cough, sore throat, chest pain, no fever
• ‘Flu-like’ with fever: Headache, loss of smell, cough, sore throat, hoarseness, fever, loss of appetite
• Gastrointestinal: Headache, loss of smell, loss of appetite, diarrhea, sore throat, chest pain, no cough
• Severe level one, fatigue: Headache, loss of smell, cough, fever, hoarseness, chest pain, fatigue
• Severe level two, confusion: Headache, loss of smell, loss of appetite, cough, fever, hoarseness, sore throat, chest pain, fatigue, confusion, muscle pain
• Severe level three, abdominal and respiratory: Headache, loss of smell, loss of appetite, cough, fever, hoarseness, sore throat, chest pain, fatigue, confusion, muscle pain, shortness of breath, diarrhea, abdominal pain

Apart from these, a link between COVID-19 and new onset diabetes has also been reported. 

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How does COVID-19 lead to diabetes?

This can be through 3 mechanisms:

• Due to stress, anxiety and depression
• Due to changes in lifestyle, consequent to the lockdown
• Direct viral injury to the pancreatic beta cells

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Through stress, anxiety and depression

It is very well known that any severe form of stress can lead to hyperglycaemia and even to overt diabetes. This form of diabetes is called as ‘stress-induced diabetes’. Following many natural disasters like earthquakes, floods, Tsunami etc. a sharp increase in  new onset diabetes have been reported. This is due to the excess counter regulatory hormones which are secreted by the blood. These counter regulatory hormones (like epinephrine, norepinephrine, cortisol, growth hormone) antagonise the action of insulin and thereby produce diabetes.

Often, after the stressful situation subsides, ‘stress-induced diabetes’ can go into a remission phase. Depression is also known to have a bidirectional relationship with diabetes. Thus, while it is known that diabetes produces depression, the reverse is also true and severe depression can lead to diabetes. Again, treatment of depression can lead to improvement in the diabetic status.

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Changes in lifestyle, consequent to the lockdown

In many parts of the world, including India, we have had extended periods of lockdown going on for several months. During this time, people stay at home and their usual physical activity is drastically reduced. Some of them also tend to overeat, because, they are bored sitting at home or due to the anxiety or depression. It has been reported that there is a marked increase in the obesity levels, both in adults and in children.

Many people who were at risk of developing diabetes, e.g. family history of diabetes, those in the pre-diabetic state etc. could have been pushed into diabetes, secondary to the irregular lifestyle, unhealthy diet, lack of exercise and increase in weight. Again, this type of diabetes can be reversed, in the early stages if the lifestyle is improved, e.g. one start exercising, eating healthy and reducing weight. 

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Direct viral injury to the pancreatic beta cells

The third and the most intriguing connection between COVID-19 and diabetes is direct injury to the pancreatic beta cells caused by the SARS-CoV-2 virus. Virus-induced diabetes is not new. It is known from earlier days that viruses like Coxsackie b4, mumps, rubella and others can cause diabetes in two ways:

• By direct injury
• By triggering auto immunity

Direct injury to the pancreatic beta cells can lead to complete destruction of the beta cells leading to severe diabetes similar to type 1 diabetes. Viruses can trigger an auto immune reaction in the pancreas leading to bets cell death and diabetes also.  There are isolated reports of such COVID-induced diabetes presenting immediately after a COVID infection with very markedly increased sugar levels. However, there are no formal studies or large series of such cases reported.

A recent report in the New England Journal of Medicine calls for setting up of registries of new onset diabetes after COVID to investigate this condition better. It remains to be seen whether such COVID-induced diabetes results due to direct injury to the pancreatic beta cells due to the virus or it acts through autoimmunity. Obviously, more studies are needed in this direction. 

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What should one do if one already has diabetes to try to prevent getting COVID-19 infection?

The most important thing is to follow all the usual precautions like social (physical) distancing, wearing a mask, avoiding crowded places and following proper respiratory etiquette. In addition to these, however those with established diabetes should ensure that their sugars are kept under good control.

Increased testing of blood sugar (self-monitoring of blood glucose – SMBG) or using Continuous Glucose Monitoring (CGM) would help to ensure that all the parameters of glycemic control are kept within limits. The fasting blood sugar should be <110 mg/dl, the postprandial blood sugar <160 mg/dl, the HbA1c less than 7% and the ‘Time in Range’ measured by continuous glucose monitoring should be over 70%. If these are ensured, then the immunity of people with diabetes could possibly improve to the levels of those without diabetes. This will ensure that even if one gets the COVID infection, it may not take a serious turn.

In the studies which have come out so far, those with uncontrolled diabetes have been shown to have worse outcomes due to COVID-19 and also to have increased mortality and morbidity. It is therefore extremely important to ensure that control of diabetes is maintained.

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This article was originally published on July 28, 2020.

Disclaimer- The views and opinions expressed in this article are those of the author's and do not necessarily reflect the official policy or position of M3 India.

The author, Dr. V Mohan is the Chairman & Chief of Diabetology at Dr. Mohan’s Diabetes Specialities Centre & Madras Diabetes Research Foundation, Chennai, India.