Brain Fog: A COVID-19 Symptom That May Linger

The term “COVID brain fog” has become a hashtag on social media, often used in a lighthearted way to denote the mental lapses that many of us are experiencing from the stress of the pandemic — finding those Brussels sprouts sitting in the oven days after you cooked them, or watching half a Netflix movie before realizing you saw it the week before.–601b47cce34f253730cf2113


But for COVID-19 long-haulers, who recover from the acute phase of the illness but continue to experience symptoms for weeks or even months, the term denotes something much more serious: It describes memory loss, concentration issues, and other cognitive problems that make it hard to get through a normal day.

Other common signs of ongoing impairment, nicknamed long-COVID, include exhaustion, body aches, and a hacking cough.

Cognitive slowing and mood problems after a person is infected with the novel coronavirus seem to be much more prevalent than with most other viral infections, says Serena Spudich, MD, a professor of neurology at the Yale University School of Medicine in New Haven, Connecticut, and a physician at Yale’s neuroCOVID-19 clinic, which opened in October. Dr. Spudich has spoken to dozens of people, some who were hospitalized with the disease and others who had only a mild case but couldn’t seem to shake their symptoms.

What Is Brain Fog?
Brain fog isn’t a technical term, but a shorthand way to describe an array of symptoms that affect thinking. Each person exhibits a different combination of issues, which can include confusion, memory loss, difficulty recalling words, slow thinking, trouble focusing, and easy distractibility.

One person who has experienced long-hauler brain fog is Fiona Lowenstein, a New York City–based TV producer and writer, who developed a case of COVID-19 last March that was severe enough to require hospitalization. The experience led Lowenstein to cofound the support group Body Politic, which now has more than 9,000 members who share over 60 channels on Slack.

Lowenstein describes a range of short-term memory issues that wreaked havoc on daily life: walking to the cabinet to get detergent while doing laundry and then forgetting why, or staring at the computer trying to write, sometimes not recalling the topic and other times grasping for the proper word.

Others on Body Politic similarly complain that the brain fog affects their work, with some struggling to stay productive and others leaving their jobs because they find it impossible to function.

No One Knows How Many People Are Affected
As with much regarding COVID-19, a disease that emerged only a year ago, the prevalence of brain fog as a long-hauler symptom is not currently known.

French researchers queried 120 patients a month after they were released from the hospital for COVID-19 complications. Some 34 percent reported continued memory loss and 28 percent said they had problems concentrating. The study was published by the Journal of Infection in August 2020.

Brain fog is now listed as a “reported long-term symptom” by the Centers for Disease Control and Prevention (CDC), albeit a less common one than fatigue, shortness of breath, cough, joint aches, or chest pain.

Why the Brain May Fog
The reasons for brain fog are not yet clear.

Spudich believes the most likely cause relates to inflammation created by the body’s immune response rather than to the virus itself. She says an overactive immune response is similarly thought to be responsible for other symptoms of COVID-19, including the breathing problems that often land patients in the hospital.

Spudich points to HIV/AIDS as another condition in which an out-of-control immune system inflames the brain, leading to mental lapses.


Meet the COVID-19 ‘Long Haulers’
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If an immune response is to blame for brain fog, it may be that inflammation in the body becomes so widespread that it reaches the brain. Or it could be that immune cells “are going into the brain to chase a little virus there,” Spudich says, noting that all this is currently conjecture.

Of course, it’s possible the virus itself somehow gets into the brain, perhaps by traveling through the top part of the nose or by infecting cells known to cross the blood-brain barrier. But so far, examinations of spinal fluid (which comes from the brain) and autopsies have not demonstrated this for the vast majority of COVID-19 cases.

The good news is that physical damage to the brain is rare, as documented by MRI images in some people.