Brain fog, other long-term COVID-19 symptoms can last for more than a year, new study finds
According to research published this week, the devastating neurological effects of long-term COVID can last for more than a year, even as other symptoms ease.
The study, published in the journal Annals of Clinical and Translational Neurology, is the longest follow-up study of neurological symptoms in long-term COVID patients who have never been hospitalized for COVID.
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Neurological symptoms — including brain fog, numbness, tingling, headache, dizziness, blurred vision, ringing in the ears, and fatigue — are the most commonly reported for the disease.
The new study, from researchers at Northwestern University, follows a shorter-term study published last spring that focused on 100 patients with long-term COVID. That study found that 85 percent of patients reported at least four lasting neurological problems for at least six weeks after their acute infection.
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For follow-up, the team continued to interview 52 original participants, who were patients in the university’s Neuro COVID-19 clinic – a long-term COVID-19 clinic – for up to 18 months.
The cohort was three-quarters female, and the mean age was 43 years. Nearly 80 percent had been vaccinated, and all had mild COVID symptoms that did not require hospitalization.
The study found that most neurological symptoms persisted after an average of 15 months.
Although most patients reported improvements in their cognitive function and fatigue, the symptoms had not completely disappeared and were still affecting their quality of life.
“Many of those patients still have problems with their cognition, which prevent them from working as they used to,” said study leader Igor Koralnik. Koralnik is the chief of neuroinfectious diseases and global neurology at Northwestern Medicine and oversees the Neuro COVID-19 clinic.
The study also found some symptoms, including variation in heart rate and blood pressure and gastrointestinal problems, that increased over time, while the loss of taste and smell tended to improve.
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The neurological symptoms — including brain fog, numbness, tingling, headache, dizziness, blurred vision, tinnitus, and fatigue — are the most commonly reported for long-term COVID. File image. Credit: Tara Moore/Getty Images
What Causes Long-Term COVID?
The Northwestern study didn’t look at why some symptoms persist, and others fade or why they occur in the first place.
“The next step for this is to find out what causes long-term COVID and why some people get it and others don’t,” Koralnik said.
Ravindra Nath, the clinical director of the National Institute of Neurological Disorders and Stroke at the National Institutes of Health, who was not involved in the new research, said one hypothesis is that symptoms in long-term COVID patients are due to damage from the inflammatory response to the coronavirus.
Any viral infection activates inflammatory cells throughout the body, including the brain. The inflammation is intended to attack the invading virus but also damages brain cells and neurons.
SARS-CoV-2, the virus that causes COVID, triggers a particularly strong inflammatory response, he said.
“COVID is probably the most serious respiratory disease we’ve ever had, so it’s no surprise that we’re seeing long-term effects from it,” Nath said.
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Panagis Galiatsatos, an assistant professor of medicine and a pulmonary and critical care physician at Johns Hopkins Medicine in Baltimore, who was not involved in the study, said it is essential to monitor ongoing symptoms to help experts with long-term COVID symptoms distinguishable from those of the natural healing process.
That, he said, will inform further research that will explore treatment and, hopefully, ways to make an early diagnosis.
Galiatsatos said it is normal for a patient to experience fatigue and other symptoms during the normal recovery after infection because fighting a virus is hard on the body. “But healing shouldn’t take six months or more,” he said.
“Right now, we need time to differentiate between the two groups,” he said.
“Patients have to wait and see, and that is very frustrating. But if we had biomarkers to test, we could identify long-term COVID and intervene early.”
However, the search for biomarkers has so far yielded no results.
In a separate study, published Monday in the Annals of Internal Medicine, researchers from another branch of the NIH — the National Institute of Allergy and Infectious Diseases — conducted comprehensive medical examinations on 189 long-term COVID patients.
The exams include more than 130 diagnostic cognitive, blood, and imaging tests. They also looked for biomarkers that would signal heart and brain damage and kidney and liver damage.
The results were compared with the same studies conducted on 120 people without long-term COVID; no differences were noted.
“Despite a thorough investigation,” said lead study author Michael Sneller, an infectious disease specialist at the NIH, “we could not show any evidence of organ damage” or other physical differences.
Sneller said that shouldn’t be interpreted as a sign that tall COVID patients aren’t experiencing actual illness. Something is happening; modern medicine has not been able to figure out what is happening until now.
“Make no mistake, these people suffer,” he said. “We’re not giving up.”