Brain fog, other long Covid symptoms can last more than a year, study finds

The devastating neurological effects of long Covid can persist for more than a year, research published Tuesday finds — even as other symptoms abate.

The study, published in the journal Annals of Clinical and Translational Neurology, is the longest follow-up study of the neurological symptoms among long Covid patients who were never hospitalized for Covid.

The neurological symptoms — which include brain fog, numbness, tingling, headache, dizziness, blurred vision, tinnitus and fatigue — are the most frequently reported for the illness.

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The new study, from researchers at Northwestern University, is a follow-up to a shorter-term study published last spring that focused on 100 patients with long Covid. That research found that 85 percent of the patients reported at least four lasting neurological problems at least six weeks after their acute infections.

For the follow-up, the team continued to survey 52 of the original participants, who were patients at the university’s Neuro COVID-19 Clinic — a long Covid clinic — for up to 18 months. The cohort was three-quarters female, and the average age was 43. Almost 80 percent were vaccinated, and all had mild Covid symptoms that did not require hospitalization.

Most neurological symptoms persisted after an average of 15 months, the study found. While most patients did report improvements in their cognitive function and fatigue, the symptoms had not gone away completely and still affected their quality of life.

“A lot of those patients still have difficulties with their cognition that prevent them from working like they used to,” said a study co-leader, Dr. Igor Koralnik, the chief of neuro-infectious diseases and global neurology at Northwestern Medicine, who oversees the Neuro COVID-19 Clinic.

The study also found that some symptoms, including heart rate and blood pressure variation, as well as gastrointestinal problems, increased over time, while loss of taste and smell tended to improve. Covid vaccination did not alleviate symptoms, but it also did not make long Covid any worse.

The Northwestern study did not look at why some of the symptoms persist and others fade away or why they occur in the first place.

“The next step for this is finding out what causes long Covid in the first place and why some people get it and others don’t,” Koralnik said.

Dr. Avindra Nath, the clinical director of the National Institute of Neurological Disorders and Stroke at the National Institutes of Health, who was not involved with the new research, said one hypothesis is that the symptoms in long Covid patients are the result of damage from the body’s inflammatory response to the coronavirus. Any viral infection activates inflammatory cells throughout the body, including in the brain. The inflammation is meant to attack the invading virus, but it also damages brain cells and neurons in the process. SARS-CoV-2, the virus that causes Covid, triggers a particularly strong inflammatory response, he said.

“Covid is probably the most severe respiratory illness we have ever had, so it’s no surprise that we are seeing long-term effects from it,” Nath said.

Dr. Panagis Galiatsatos, an assistant professor of medicine and a pulmonary and critical care doctor at Johns Hopkins Medicine in Baltimore, who was not involved with the study, said continuing to track lasting symptoms is crucial to help experts separate long Covid symptoms from those of the natural healing process. That, he said, will inform further research that will explore treatment and, hopefully, ways to provide an early diagnosis

Galiatsatos said it is normal for a patient to experience fatigue and other symptoms during the normal recovery process after an infection, because fighting off a virus is hard on the body. “But healing shouldn’t last six months or more,” he said.

“Right now we need time to distinguish between the two groups,” he said. “Patients have to just wait, and that’s really frustrating. But if we had biomarkers to test, we could identify long Covid and intervene early.”

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The search for biomarkers, however, has yielded no results so far.

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 — carried out comprehensive medical exams on 189 long Covid patients.

The exams included more than 130 cognitive diagnostics, blood and imaging tests. They also looked for biomarkers that would signal heart damage and brain damage, as well as kidney and liver injury.

The results were compared to the same exams carried out in 120 people without long Covid; no differences were identified.

“Despite a thorough investigation,” said the lead study author, Dr. Michael Sneller, an infectious disease specialist at the NIH, “we could not demonstrate any evidence of organ damage” or other physical differences.

That should not be interpreted to mean long Covid patients are not experiencing true illness, Sneller said. Something is occurring; modern medicine simply has been unable so far to figure out what is going on.

“Make no mistake, these people are really suffering,” he said. “We’re not giving up.”

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