• Robert Preidt
• Posted January 20, 2022

New Clues to Why Some Develop 'Brain Fog' After COVID

Brain fog. It has become an inexplicable side effect of COVID-19 infection, but researchers now report they have discovered a possible reason why it happens.

In a small study, investigators found abnormalities in the cerebrospinal fluid of some COVID-19 patients who developed thinking problems.

The symptoms "manifest as problems remembering recent events, coming up with names or words, staying focused, and issues with holding onto and manipulating information, as well as slowed processing speed," explained study senior author Dr. Joanna Hellmuth, from the Memory and Aging Center at the University of California, San Francisco.

Brain fog is a common aftereffect of COVID infection, striking about 67% of 156 patients at a post-COVID clinic in New York, a recent study found.

In this latest study, the researchers analyzed the cerebrospinal fluid of 13 people who had thinking and memory problems after COVID-19 and of four recovered COVID-19 patients with no cognitive symptoms.

The average age of those with cognitive symptoms was 48, compared with 39 for those with no cognitive symptoms. The cerebrospinal fluid samples were collected an average of 10 months after the patients' first COVID-19 symptoms. None of the patients were hospitalized for COVID-19.

Cerebrospinal fluid anomalies were found in 10 of the 13 patients with cognitive symptoms, but not in any of the four with no cognitive symptoms, according to the study published Jan. 19 in the journal Annals of Clinical and Translational Neurology.

The cerebrospinal fluid of patients with cognitive symptoms had elevated levels of protein, suggesting inflammation, as well as unexpected antibodies found in an activated immune system.

Some of those antibodies were found in both cerebrospinal fluid and blood, indicating a systemic inflammatory response, or were found only in cerebrospinal fluid, suggesting brain inflammation.

While the targets of these antibodies are unknown, they could be "turncoat" antibodies that attack the body itself, according to the researchers.

"It's possible that the immune system, stimulated by the virus, may be functioning in an unintended pathological way," said Hellmuth, who is principal investigator of the UCSF Coronavirus Neurocognitive Study and is also affiliated with the UCSF Weill Institute for Neurosciences.

"This would be the case even though the individuals did not have the virus in their bodies," she said in a university news release.

The study also found that participants with thinking problems had an average of 2.5 risk factors for impaired thinking, compared with an average of less than one risk factor for participants without the symptoms.

Those risk factors included: diabetes and high blood pressure, which can increase the risk of stroke, mild cognitive impairment and vascular dementia; a history of attention deficit hyperactivity disorder (ADHD), which may make the brain more vulnerable to executive functioning issues; anxiety; depression; a history of heavy alcohol or repeated stimulant use; and learning disabilities.

More information

For more on COVID-19 brain fog, go to Harvard Medical School.

SOURCE: University of California, San Francisco, news release, Jan. 18, 2022