For Long COVID sufferers who have faced scepticism and shrugs from healthcare providers or disability claims offices, here is some encouraging news. Two small but significant studies have uncovered data that reveal potential biomarkers for Long COVID. Biomarkers offer researchers and clinicians a way to objectively determine who has a specific disease, and measure whether or not and how much that person’s condition improves after an experimental treatment.*

Levels of cortisol in the blood

The first study, conducted by researchers at Yale and Mount Sinai, compared blood samples of 273 people who fell into three categories: 

• Those diagnosed with Long COVID, 
• Those who had COVID-19 but are thought to have fully recovered, and
• Those with no evidence of having had the infection.

Of those who’d had infections, most had mild initial illnesses. The most common symptoms reported included:

• Brain fog and memory issues,
• Fatigue and post-exertional malaise,
• Postural orthostatic tachycardia syndrome (POTS).

The research team found that the blood samples from people with Long COVID contained lower levels of the hormone cortisol in the early part of the day. In fact, their levels were approximately half of the morning cortisol levels of people in the control groups. Cortisol levels are usually highest in the morning, to help us wake up and start our day, and lowest at night, when the body is winding down toward rest.

“Seeing that folks with Long COVID have this blunted morning cortisol peak was really interesting when you think about their symptoms of fatigue and post-exertional malaise,” said study author Dr. David Putrino, director of rehabilitation innovation for the Mount Sinai Health System.

“When you have low levels of cortisol, you will get tiredness, nausea, vomiting, weight loss, weakness, and pain,” added Dr. Akiko Iwasaki, an immunobiologist at Yale School of Medicine. Since those are frequently experienced by COVID long-haulers, she noted, “lower levels of cortisol could be contributing to the symptoms.”

MRI scans show organ damage

The second study, conducted by researchers from Oxford, used magnetic resonance imaging (MRI) to scan 259 people who had been hospitalized due to COVID-19. An average of five months after their discharge, one out of three patients showed evidence of damage to their lungs, brain or kidneys, though no lasting damage to their hearts or livers.

While lung injuries were linked to ongoing symptoms of chest tightness and cough, damage to other organs didn’t always correspond to individuals’ symptoms. People with MRI evidence of damage to two or more organs, however, were four times more likely to report severe disability, both physical and mental.

“There’s now concrete evidence,” said Christopher Brightling, a professor of respiratory medicine at the University of Leicester, “that there are changes in a number of organs following COVID infection in people who’ve been hospitalized.”

What does it all mean?

Ultimately, the results from the two studies could help doctors determine which tests might be most useful for accurately diagnosing Long COVID. 

“That’s what a lot of patients would love,” said Dr. Daniel Griffin, an infectious disease expert at Columbia University who treats patients with Long COVID but was not involved in the new studies. “This is some validation for the community that this isn’t just a bunch of people who are complaining a lot. They would like to know ‘what blood tests can I get to confirm I have Long COVID?’” 

Griffin added that, while researchers aren’t quite there yet, these studies give them important evidence to build upon.

*Goodman, B. (2023, September 25). Scientists edge closer to finding a biomarker for long Covid. CNN. https://www.cnn.com/2023/09/25/health/long-covid-studies-test-treatment-development-wellness/index.html