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Cleveland Clinic analysis provides new details on effects of COVID-19 on diabetes, blood sugar

Researchers found that, despite previous reports, blood sugar increases were not significantly different in COVID-19 positive and negative patients.


Cleveland Clinic research suggests higher rates of Type 2 diabetes in COVID-positive patients might be due to getting diagnosed during care – not a sudden spike in blood sugar levels.

Researchers analyzed blood sugar rates over time in patients who tested positive for COVID-19 and those who tested negative to address questions about how the virus affects the pancreas and blood sugar regulation. The findings, published in Diabetes, show the difference between COVID-positive and COVID-negative patients was clinically insignificant, despite COVID-positive patients being 40% more likely to be diagnosed with Type 2 diabetes.

“The results suggest the COVID-positive patients could have been less likely to receive a Type 2 diabetes diagnosis if they had tested negative, just due to the extra clinical attention they receive during COVID management,” says Daniel Rotroff, PhD, Department of Quantitative Health Sciences.

The investigation provides important perspective for clarifying the long-term effects of COVID-19. Type 2 diabetes, which impairs the body’s ability to process sugars for energy, is already regarded as a risk factor for severe illness from COVID-19. More than 37 million Americans have diabetes, with Type 2 diabetes making up 90-95% of people with the condition.

The pancreas plays an essential role in regulating blood sugar levels by producing insulin. The pancreas can become inflamed in COVID-19 patients, with some contracting acute pancreatitis. The virus was also found in pancreatic cells that produce insulin. Coupled with a trend of patients developing Type 2 diabetes after diagnosis, this evidence sparked concern in the medical community about COVID-19 causing Type 2 diabetes.

Addressing COVID-19 diabetes questions with statistical analysis

Previous studies suggested the disease may impact glycemic function, but those studies lacked a negative control – a pool of similar patients that are COVID-negative.  The Cleveland Clinic team investigated this further by comparing patients that tested positive for COVID-19 to a large population that tested COVID-negative, Dr. Rotroff said.

The analysis used Cleveland Clinic data from more than 20,000 patients, pulling information for a blood sugar test called HbA1c. The patients included in the study were not necessarily seeking out care for COVID-19 symptoms – some tested positive during screenings for another procedure.

Researchers analyzed blood test information from up to a year between the last blood sugar test and a positive or negative COVID-19 test to see whether blood sugar levels spiked near a COVID-19 diagnosis.

“Previous studies have shown that patients’ HbA1c levels tend to go up after testing positive for COVID-19,” Dr. Rotroff says. “We observed the same thing. However, HbA1c also goes up over time in patients that tested negative for COVID-19, which means it is probably just a general characteristic rather than anything due to COVID.”

What patients should know

The study highlights the importance of routine medical care and undergoing recommended screenings, says Kevin Pantalone, DO, a co-author on the study and Director of Diabetes Initiatives in Cleveland Clinic’s Department of Endocrinology.

People might get tested when they are presenting diabetes symptoms, but some people with Type 2 diabetes don’t show symptoms. Type 2 diabetes is often caught when patients are getting care for other diseases – like COVID-19.

The United States Preventive Services Task Force recommends screening for adults aged 35 to 70 years who have overweight or obesity.

“When patients do not interact with the healthcare system regularly, this essential screening is not performed, leading to a missed opportunity to diagnose the disease early,” Dr. Pantalone says. “Unfortunately, this is very common, with the medical literature suggesting that patients with Type 2 diabetes have had the condition for about 5 years prior to the formal diagnosis being made.”

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