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New research finds a significant association between signs of blood clotting and symptoms of long COVID. Morsa Images/Getty Images
  • A new study finds that long-haul COVID-19, commonly referred to as “long COVID,may be related to blood clotting issues.
  • In the study, 50 people were reviewed for an average of 68 days after developing COVID-19.
  • They found people with higher blood clotting markers were more likely to have long COVID symptoms.

While most people with COVID-19 get better within weeks, some people experience post-COVID-19 conditions that are commonly dubbed “long COVID” or long-haul COVID-19.

Post-COVID-19 conditions are a wide range of new, returning, or ongoing health problems that may be experienced 4 or more weeks after getting COVID-19, according to the Centers for Disease Control and Prevention (CDC).

Researchers still aren’t sure what causes these long-term symptoms.

Now, new research finds that people with long COVID show higher measures of blood clotting, which could help explain persistent symptoms, including reduced physical fitness and fatigue.

The study, led by researchers from RCSI University of Medicine and Health Sciences in Dublin, was published this month in the Journal of Thrombosis and Haemostasis.

For the study, 50 people were reviewed for an average of 68 days after developing COVID-19 to better understand the role blood clotting might play in long-hauler symptoms.

Their findings indicated that signs of clotting, called clotting markers, were significantly elevated in the blood of people with long COVID symptoms, compared with healthy people in a control group.

Although clotting markers were significantly higher in those hospitalized due to their initial illness, researchers found that even patients who remained at home had high clotting markers.

It’s still too early to know what the correlation is between blood clotting and long COVID, or what the causes and effects of these higher clotting factors are, according to Dr. Teresa Murray Amato, the director of emergency medicine at Long Island Jewish Forest Hills New York.

“However, it is important to try and make these connections,” she said, “to better understand how to counsel patients who are suffering long after their initial COVID infection.”

“Long COVID is a still poorly defined syndrome that occurs after the acute viral infection due to COVID has passed,” said Dr. Thomas Gut, the associate chair of medicine and director of the Post-COVID Recovery Center at Staten Island University Hospital in New York.

“Predominantly it is categorized by persistent cognitive changes and fatigue symptoms, but newer strains have shown newer symptoms that have not been seen earlier in the pandemic,” he continued.

Gut emphasized that the most effective option available to prevent, and possibly treat, long-haul COVID-19 is the COVID-19 vaccine.

“Not only does vaccination reduce the risk of severe infection,” he said. “But it also has potential to help reduce the risk of contracting COVID in the first place.”

Amato said, in her experience with people with long COVID, she has seen a variety of symptoms.

“After the first wave of the pandemic, we were seeing patients presenting weeks and months after COVID-19 infections with varied complaints,” she said.

Amato said these long-term symptoms include:

  • fatigue
  • shortness of breath
  • palpitations
  • lingering loss of taste and smell
  • anxiety

She said that, up until recently, it was “very difficult” to know which people with COVID-19 would experience long COVID.

However, this recent study noted a correlation between elevated clotting markers and long-term effects, offering important information.

“The theory is that, somehow, the increased clotting factors can be an indication used to identify patients who are at a higher risk of long-term COVID symptoms,” Amato said.

According to the study, researchers found that increased blood clotting was directly related to other symptoms of long COVID, including reduced physical fitness and fatigue.

Researchers also found that, while markers of COVID-19-related inflammation had all returned to normal levels, this increased clotting potential was still present in people experiencing long COVID.

“Because clotting markers were elevated while inflammation markers had returned to normal, our results suggest that the clotting system may be involved in the root cause of long COVID syndrome,” Dr. Helen Fogarty, the study’s lead author, ICAT fellow, and PhD student at the RCSI School of Pharmacy and Biomolecular Sciences, said in a statement.

The study authors pointed out that autopsies of people who died of COVID-19 have shown inflammation in the cells that line the heart and blood cells (endothelial cells), and that blood clotting in the vascular system triggered by the immune response plays a key role in severe COVID-19.

They believe that activation of these cells may also contribute to long COVID.

Gut said that, as more people contract the coronavirus, we’re seeing a steady rise of patients experiencing long COVID symptoms.

“Most alarmingly,” he warned, “the patients we see with these long-term health effects are getting younger as new mutations arise from the original strain.”

He added that the exact mechanism of clotting is still being investigated, but the growing consensus is that COVID-19 activates the body’s natural clotting pathways in tissues where the disease has caused significant inflammation.

According to Gut, there are only a few treatment options for long COVID patients.

“Generally, these treatments are tailored to address specific symptoms and complaints,” he said. “Fortunately, most symptoms from long COVID do resolve on their own with monitoring for complications.”

New research has found a significant association between signs of blood clotting and the symptoms of long COVID, even in patients who were never hospitalized during their illness.

Experts say that long COVID is still poorly understood, and these findings may help identify people at risk of experiencing long-term symptoms.

They also warn that people with long COVID are getting younger, while variants are causing new long-term symptoms — and, crucially, that COVID-19 vaccination is the best way to prevent illness, which will prevent long COVID.