There are a lot of potential side effects of COVID-19 that experts are still learning about, and it's been hard to pinpoint which are actually due to COVID-19 and which may simply be coincidence. But there's one in particular that keeps coming up: brain fog. Now, a new study suggests this could actually be a consequence of having COVID-19.
The study, which was published on October 22 in JAMA Network Open, analyzed data from 740 people with a mean age of 49 who had COVID-19 within about the past 7 and a half months. The researchers found that a significant portion had some kind of cognitive deficit (in other words, trouble thinking), like brain fog. The most common issues were memory encoding, i.e. learning new information, and memory recall, which happened in 24% and 23% of study participants, respectively. The researchers also found that those who were hospitalized with COVID were at greater risk than those who stayed in an outpatient setting.
The research branched off of data that the Icahn School of Medicine at Mount Sinai has been collecting since April 2020 on COVID-19 patients, lead study author Jacqueline H. Becker, PhD, a clinical neuropsychologist and associate scientist in the Division of General Internal Medicine at the Icahn School of Medicine at Mount Sinai in New York City, tells Health. "We started to see that, over time, so many patients complained of these residual difficulties," she says. "We just wanted to get a sense of what was going on."
Becker says she and her colleagues originally thought they would be looking at older patients, but realized that most of the people who experienced cognitive issues was "fairly young."
The brain fog Becker is studying falls under the umbrella of post-COVID, aka long COVID, a mysterious group of conditions people can develop after having COVID-19. The Centers for Disease Control and Prevention (CDC) notes that post-COVID conditions can show up four or more weeks after the virus is contracted. The CDC acknowledges that many symptoms can fall under long COVID, including the following:
Difficulty breathing or shortness of breath
Tiredness or fatigue
Symptoms that get worse after physical or mental activities
Chest or stomach pain
Fast-beating or pounding heart
Joint or muscle pain
Dizziness on standing
Change in smell or taste
Changes in menstrual period cycles
"There are a lot of hypotheses, but we really don't have the answer just yet," Becker says. One possible cause is that SARS-CoV-2, the virus that causes COVID-19, may directly invade the central nervous system and brain. "We've seen this in some autopsy studies, but those are obviously biased because they're in people who didn't survive COVID," Becker says.
Another theory is that the brain fog may be a result of the virus causing chronic inflammation, even after a person has recovered from COVID-19. "That tends to be the most likely at this point," Becker says. The final theory, Becker says, is that someone may develop hypoxia, or lack of oxygen to bodily tissues like the brain, when they have the virus, leaving them with aftereffects like brain fog.
But, again, it's really hard to say. "Cognitive dysfunction is likely multi-factorial and may be a result of direct viral effects on the central nervous system, immune effects, some baseline risk factors or a combination of all," infectious disease expert Amesh A. Adalja, MD, senior scholar at the Johns Hopkins Center for Health Security in Maryland, tells Health. "In severe patients, sedatives and other ICU medications may play a role."
One thing that is certain, though, is that brain fog isn't a rare thing. Dr. Adalja has seen it, and so has Richard Watkins, MD, an infectious disease physician and professor of internal medicine at the Northeast Ohio Medical University who treats COVID patients. "This is another reason to get vaccinated," Dr. Watkins tells Health.
Becker says that you should "definitely" let your primary care physician know what's going on. It's also a good idea to see if there's a post-COVID care center somewhere in your area. "If it's available, get a formal evaluation," Becker says. You also may want to see a neuropsychologist so you can be evaluated and tracked over time, she says.
Just know this, per Becker: "We don't know if certain treatments for cognitive impairment like cognitive rehab will be helpful for this population."
It's unclear. "It likely dissipates over time in most patients," Dr. Adalja says, adding, "this is an area of active study." Becker agrees. "We're still learning so much about this," she says. Her particular research looked at patients after an average of seven and a half months and still found a "high level of impairment." But, she points out, "it could resolve after, say, 10 months or last much longer."
While there are a lot of unknowns right now, Becker and her team are continuing to research brain fog after COVID-19 and hope to have more answers at some point.