What does a deep dive into the immune system of people with long COVID reveal?


New study alert! A recent study available as a preprint found multiple biologic similarities in people experiencing long COVID.

This early research informs future studies on the diagnosis of long COVID using self-reported symptoms and laboratory data as well as potential target mechanisms for the treatment of this debilitating condition.

The underlying cause of long COVID remains poorly understood. Long COVID symptoms vary from person to person and persist more than 3-6 weeks after the initial infection. The symptoms disrupt daily life. For some, this might mean the inability to return to exercise or work, increased requirements for sleep, or difficulty concentrating. Others may not be able to leave bed due to the severity of their symptoms. Either way, the condition is scary, uncomfortable, and difficult to treat without a better understanding of what might cause it. A recent study took a deep dive into the blood of people with long COVID symptoms to understand what may be causing the symptoms.

The study found that self-reported symptoms of long COVID accurately predicted disease in 94% of study participants. Long COVID was defined in this study as persistent symptoms 6 weeks after initial COVID-19 infection. On average, long COVID participants in the study had been infected more than one year prior to the study. The comparison groups included people who never had COVID-19 and people who had fully recovered from COVID-19. The most common reported long COVID symptoms included fatigue, brain fog, and memory difficulty. Nearly 38% of participants with long COVID had a diagnosis of Postural Orthostatic Tachycardia Syndrome, also known as POTS. When people with POTS sit up or stand, they experience increased heart rates that can cause shortness of breath, passing out, and severely limited activities of daily living. Moving forward, this study further supports the need to ask people about symptoms after COVID-19 infection as a useful indicator for the diagnosis of long COVID.

This study supports findings in other studies pointing to low cortisol levels as an underlying mechanism of long COVID. This study found a strong relationship between low cortisol levels in the long COVID participants when compared to people who fully recovered from or never had COVID. Cortisol is a stress hormone that is involved in the regulation of your sleep cycle, glucose or sugar regulation in your body, and inflammation or swelling in your body. Low cortisol levels may be a useful tool in diagnosing long COVID and predicting severity of illness.

The study also identified multiple biologic markers that are present with consistency in people with long COVID. People with long COVID had T cells that appear to be fighting something for extended periods of time. T Cells are one type of defender in your immune system. This type of exhausted T cell reaction is common with reactivation of herpes viruses including Epstein Barr (the virus that causes mono) and Varicella Zoster (the virus that causes shingles). Overall, the study identified several important biologic differences in the blood of people with long COVID worthy of further study.

Estimates of the number of people experiencing long COVID vary, though it affects millions of people in the US and globally. The condition disrupts overall health, daily life, workplaces, and caregiving. This study adds to the body of knowledge about what might cause long COVID symptoms and opens doors to new research on treatment options. The current manuscript is a preprint, meaning it has not gone through peer review. Those Nerdy Girls will continue to share new findings as they become available.

Additional Resources:

Summary of Preprint Study in Nature

Twitter thread explaining the original article by senior researcher Dr. Akiko Iwasaki

Original Preprint Study “Distinguishing features of Long COVID identified through immune profiling”

Link to Original FB Post