According to the largest study of its kind, contracting COVID-19 may increase the risk of developing an autoimmune disease by 43 percent in the months following the infection, Live Science reported this week.
According to Anuradhaa Subramanian, a research fellow in health informatics at the University of Birmingham, who was not involved in the study, "The impact of this study is huge — it's the strongest evidence so far answering this question of COVID-19 and autoimmune disease risk."
The study, which has not yet been peer-reviewed, was published on January 26 in the preprint database medRxiv.
Previous research has linked COVID-19 to an increased risk of autoimmune disease, a condition in which the immune system mistakenly attacks healthy parts of the body. However, these studies were limited to small samples and focused on specific conditions, such as autoimmune hemolytic anemia, which affects red blood cells, and Guillain-Barre syndrome, which affects nerve cells, the outlet reported.
But this new study analyzed the medical records of 640,000 people in Germany who tested positive for COVID-19 in 2020 and 1.5 million people who did not contract the virus to investigate the potential impact on the development of 30 autoimmune conditions. This is a much larger study than previous research, which focused on smaller cohorts and fewer conditions.
In order to explore the potential impact of COVID-19 on the risk of developing autoimmune conditions, researchers analyzed the health records of 640,000 individuals in Germany who had contracted the virus in 2020, as well as 1.5 million individuals who did not catch the coronavirus that year. The study examined the rate at which newly diagnosed autoimmune diseases occurred in the three to 15 months following a positive COVID-19 test, comparing these rates to those of the group that did not contract the virus. Approximately 10 percent of participants in each group had preexisting autoimmune diseases.
The study found that among those without a history of autoimmune disease, more than 15 percent of those who contracted COVID-19 developed an autoimmune condition for the first time during the follow-up period, compared to roughly 11 percent of those who did not contract the virus. In other words, the COVID-19 group had a 43 percent higher risk of developing an autoimmune disease compared to the control group. Among those with preexisting autoimmune conditions, the group that contracted COVID-19 had a 23 percent higher risk of developing an additional autoimmune disease during the follow-up period.
The research found that COVID-19 was most strongly associated with an increased risk of vasculitis, a condition that involves inflammation of the blood vessels. The group that had previously contracted the virus had a 63 percent higher rate of a specific type of vasculitis called arteritis temporalis compared to the uninfected group. Prior COVID-19 infection was also strongly linked to autoimmune-driven issues with the thyroid, psoriasis, and rheumatoid arthritis, a condition that causes joint swelling, the report continued.
"These findings just cannot be ignored," Subramanian noted, according to Live Science. "We need to pursue research into how COVID-19 is potentially triggering autoimmunity because many people are continuing to suffer from the effects of COVID-19."
According to the researchers, there are various hypotheses as to how COVID-19 could initiate autoimmunity, and it is possible that different mechanisms may impact different organ systems.
"Understanding how COVID-19 impacts autoimmune disease risk will help in executing the prevention measures and early treatments to prevent associated morbidity and mortality," said Jagadeesh Bayry, a professor of biological sciences and engineering at the Indian Institute of Technology Palakkad, who also wasn't involved in the study.
Noted Live Science: "Other viral infections, including influenza, have been linked to autoimmune disease, so more research is needed to establish what effects are specific to COVID-19," Bayry said.
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