People who get COVID-19 have a higher risk of developing diabetes up to a year later, even after a mild SARS-CoV-2 infection, compared to those who have never had the disease, a massive study1 of nearly 200,000 people show.
The research, published in The Lancet Diabetes & Endocrinology earlier this month is one of a growing number of surveys2 shows that COVID-19 can increase a person’s risk of diabetes, months after infection.
“When this whole pandemic disappears, we will be left with the legacy of this pandemic – a legacy of chronic disease” that health systems are not prepared for, says study co-author Ziyad Al-Aly, chief researcher at Veterans Affairs (VA) St Louis Healthcare System in Missouri.
Risks are amplified
Al-Aly and Yan Xie, an epidemiologist also at the VA St. Louis Healthcare System, looked at the medical records of more than 180,000 people who had survived for more than a month after catching COVID-19. They compared these with records from two groups, each involving about four million people without SARS-CoV-2 infection who had used the VA health care system, either before or during the pandemic. The couple previously used a similar method to show that COVID-19 increases the risk of kidney disease3, heart failure and stroke4.
The latest analysis showed that individuals who had had COVID-19 were about 40% more likely to develop diabetes up to a year later than veterans in the control groups. This meant that for every 1,000 people examined in each group, about 13 more people in the COVID-19 group were diagnosed with diabetes. Almost all cases were type 2 diabetes, in which the body becomes resistant to or does not produce enough insulin.
The chance of developing diabetes increased with increasing severity of COVID-19. People who were hospitalized or hospitalized in intensive care had roughly tripled the risk compared to controls who did not have COVID-19.
Even people who had mild infections and no previous risk factors for diabetes had increased chances of developing the chronic condition, Al-Aly says. Of the people with COVID-19 who avoided hospitalization, an additional 8 people out of every 1,000 patients had developed diabetes a year later compared to people who were not infected. People with a high body mass index, a measure of obesity – and a significant risk factor for type 2 diabetes – were more than twice as likely to develop diabetes after a SARS-CoV-2 infection.
Given the extraordinary number of COVID-19 cases globally – 480 million confirmed cases and counting – the modest increase in diabetes risk could equate to a drastic increase in the number of people diagnosed with the disease worldwide if the observed trends hold true, says Jonathan Shaw , an epidemiologist at the Baker Heart and Diabetes Institute in Melbourne, Australia.
But the results can not translate to other groups of people. The American veterans in the study were mostly elderly, white men, many of whom had high blood pressure and were overweight, which put them at high risk of developing diabetes, says Gideon Meyerowitz-Katz, an epidemiologist studying diabetes at the University of Wollongong in Australia . But that risk is much lower in younger people, he says, and higher in some other ethnic groups.
And it is possible that some individuals in the control group had undetected mild or asymptomatic COVID-19 but were never tested, potentially skewing the data, Al-Aly adds.
Other factors may also contribute to the apparent increase in diabetes among people who recovered from COVID-19, Shaw says. Existing cases of diabetes may have gone undetected until people sought medical help for COVID-19.
Early in the pandemic, researchers raised concerns based on anecdotal reports in adolescents and children that SARS-CoV-2, like other viruses, can damage pancreatic cells that produce insulin, triggering type 1 diabetes.
However, data on an association between SARS-CoV-2 infection and newly diagnosed cases of type 1 diabetes remain mixed. More studies5–7 have found no evidence that the disease causes the increase in cases of type 1 diabetes in younger adults or children. And a laboratory study published in February also challenged the idea that SARS-COV-2 destroys insulin-producing pancreatic cells8.
A remaining question is whether the metabolic changes observed in individuals who had COVID-19 continue after one year. More research is needed to clarify long-term trends in emerging diabetes at the population level and to tease apart what may be causing them, Shaw says.