Long COVID Brain Fog: What It Is and How to Manage It

“Brain fog” is one of the most debilitating problems experienced by people with Long COVID, a condition in which COVID-19-like symptoms continue or develop after the acute infection has passed. People who experience brain fog say they have an inability to think clearly, are forgetful, and can’t focus their attention or find the right words in a conversation.

An estimated 7% of adults—or about 17 million people—in the United States reported having Long COVID in March 2024, based on data from the Centers for Disease Control and Prevention (CDC). Estimates vary as to exactly how many of those people struggle with cognitive function, but in one study of people with Long COVID, close to half reported having poor memory or brain fog.

For most people, Long COVID brain fog eventually goes away, but it still can have a life-altering impact. “It’s definitely not subtle,” says neurologist Lindsay McAlpine, MD, who directs the Yale Medicine NeuroCovid Clinic and works with neurologist Serena Spudich, MD, MS, to research Long COVID-related cognitive dysfunction. “People have told me they used to be amazing at multitasking, but with brain fog they can do only one thing at a time. Other patients have switched jobs because they could no longer handle the tasks, stress, or thought-load of their previous job.”

There is no cure for Long COVID or brain fog, but experts are learning more about how to care for patients who have it, Dr. McAlpine adds.

Below, Yale Medicine and Yale New Haven Health providers answer questions about Long COVID brain fog and what to do about it.

Brain fog isn’t an official medical diagnosis; rather, it’s a colloquial term for a range of significant, persistent neurocognitive impairments that cause such symptoms as sluggish thinking, difficulty processing information, forgetfulness, and an inability to focus, pay attention, or concentrate. With Long COVID, the exact combination of brain fog symptoms varies from one person to the next.

The condition can affect anyone who has had COVID, regardless of their age or the severity of their initial COVID infection. Brain fog is considered a Long COVID symptom if it’s present three months after the person had COVID and has persisted for more than two months, Dr. McAlpine says. It usually goes away completely between six and nine months after the infection, although in some people it lasts as long as 18 months or more, Dr. McAlpine says.

Scientists don’t yet have a solid understanding of what causes Long COVID brain fog. One theory is that the SARS-CoV-2 virus that causes COVID persists in the gut after the acute infection has cleared up, and changes in the gut have been associated with changes in brain function. Dr. McAlpine also cited a small study published in February 2024 in Nature Neuroscience that used a specialized type of MRI (called dynamic contrast-enhanced magnetic imaging) to show that some Long COVID patients with brain fog have dysregulation in the blood-brain barrier, a network of tissue and blood vessels that protects the brain from harmful substances.

There is no single test to confirm that a person has Long COVID, and the same is true for brain fog. But a neurological exam and cognitive testing can identify deficits in a person’s brain function. Similarly, there is no specific cognitive screening test for people with Long COVID, but a number of tests used to evaluate conditions like dementia can help determine whether a person is experiencing it, Dr. McAlpine says. “We look for deficits in language, working memory, declarative memory [a type of long-term memory], motor function, and perception,” she says.

It helps to know if a patient has other Long COVID symptoms, which are wide-ranging and can include fatigue, difficulty breathing, heart palpitations, headache, stomach pain, and joint pain, among others, she adds.

Yes, some people develop new conditions when they have Long COVID; the condition can also worsen existing conditions and “unmask” diseases that were there previously but undiagnosed, Dr. McAlpine says. “This is why the patient's story and clinical history really matter, because if the brain fog doesn’t link up with COVID, then we have to think about different causes,” she says.

Bloodwork, including a complete blood count and comprehensive metabolic panel, helps rule out such problems as a thyroid condition or vitamin B-12 deficiency that are known to cause cognitive symptoms. Syphilis and human immunodeficiency virus (HIV) are also conditions to test for, depending on the patient’s risk for those conditions, Dr. McAlpine says.

"Obstructive sleep apnea (OSA) is another potential cause for cognitive dysfunction, and is often diagnosed in people with Long COVID," Dr. McAlpine says. “Or they had sleep apnea before and it was tolerable for them, but after COVID they became much more sensitive to it and had more symptoms.”

Likewise, a subset of patients in Dr. McAlpine’s practice had either diagnosed or undiagnosed attention-deficit/hyperactivity disorder (ADHD) before COVID, and Long COVID caused a “dramatic worsening” of their ADHD symptoms, including the forgetfulness and lack of focus also associated with brain fog, she says. “Some found that the medication they had been taking for ADHD stopped working for them,” she says. “I’ve also cared for people who had always suspected they had ADHD, but they were high-functioning and coped. Their coping skills stopped working with Long COVID.”

There are other conditions, such as chronic fatigue syndrome, and postural orthostatic tachycardia syndrome (POTS), that are associated with cognitive dysfunction independent of Long COVID. “In individuals with brain fog who have these syndromes as part of their Long COVID, the brain fog may not improve until we address these conditions,” Dr. McAlpine says.

Long COVID brain fog clears up in the majority of people who have it, but lifestyle practices can help, Dr. McAlpine says. For instance, “exercise is one thing we know boosts cognition in most individuals, even in patients with dementia,” she says.

But it’s important to approach exercise carefully, especially for people with certain conditions, including myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) [a neuroinflammatory, neuroimmune illness most commonly triggered by infection, causing severe fatigue and other symptoms]. “Individuals with ME/CFS after COVID-19 can also experience brain fog and should take precautions when exercising, most importantly avoiding post-exertional malaise [PEM] by pacing and working closely with their physical therapy and medical teams,” she says. (PEM is fatigue and worsening of symptoms after physical and mental exertion.)

“There is also a mood component, which is important,” Dr. McAlpine adds, explaining that many people with brain fog symptoms also experience depression or anxiety, and those who had mental health conditions before may notice them getting worse. “But, if a mental health problem is diagnosed, it needs treatment.”

In addition, Dr. McAlpine says many of her patients have responded well to two medications—N-acetylcysteine (NAC) and guanfacine.

In 2020, Arman Fesharaki-Zadeh, MD, PhD, a Yale Medicine behavioral neurologist and neuropsychiatrist, discovered that the medications could help Long COVID patients with brain fog, when he realized that one of his Long COVID patients was having cognitive symptoms that were similar to patients with a history of traumatic brain injury (TBI) who were suffering from post-concussive syndrome. NAC was being tested for the treatment of TBI and also helped with cognitive deficits. He added guanfacine, which was developed by Yale neuroscientist Amy Arnsten, PhD, and had been used to treat ADHD.

The two published a small study in the Nov. 2023 issue of Neuroimmunology Reports, and now researchers are hoping for funding for larger clinical trials. In the meantime, NAC is available over-the-counter, and patients may be able to get a prescription for guanfacine off-label from their doctor.

"There has also been evidence of COVID vaccines helping with Long COVID symptoms like brain fog, but there are no guarantees," Dr. McAlpine says. “We had many patients in our first wave of COVID who had bad brain fog after COVID, and their symptoms improved with their first vaccination. But I've seen that happen less lately, possibly because more people are vaccinated. That may have been more of a ‘first wave’ phenomenon."

While some people experience more severe brain fog than others, many find there are strategies that can help, says Kaleigh Frame, MA, CCC-SLP, a Yale New Haven Health speech-language pathologist who has cared for Long COVID patients who have already been seen by a Yale Medicine neurologist. She provides strategies based on the types of cognitive deficits they are struggling with.

First, she teaches patients to build “self-advocacy skills,” such as letting other people know about their limitations due to brain fog. She also helps with “metacognition,” which she describes as a person’s ability to assess their own cognitive skills. For instance, they decide how they are doing at different times on a scale of 1 to 10 and record their numbers on a calendar or notes app. “This can help determine whether there are patterns of brain fog throughout the day, and it can also help track progress or decline,” she says. “Then, the next time you follow up with your neurologist, it won’t be vague, because you have a written log you can refer to.”

Yet another strategy is having a “brain budget,” which involves estimating how much mental energy you have in a given day (based on your records) and prioritizing when and how to best use it, making sure you have time for breaks so your brain power is not used up too quickly. "A person might say, ‘I can do all six of these things, but in between, I need recovery breaks,’” Frame says.

Frame also has specific advice for the following brain fog issues:

• Memory difficulties: Try visualization techniques (picturing the thing you want to remember in your head), auditory rehearsal (repeating the thing, such as a short list, in your head), and active listening (repeating back what a person you are talking to has said). She suggests people use these techniques for specific functional tasks they see as priorities in their day.
• Inability to focus: During moments of brain fog, take “a low-stimulation break,” Frame says. Find a quiet, maybe darker environment in another room (if possible), put down the phone, close your eyes, and set a timer for a few minutes to regroup. One approach is to do this four times a day to prevent brain fog rather than using breaks as a time to recover from feeling overwhelmed.
• Difficulty finding the right word: One strategy is called semantic feature analysis. “You have a target—whatever the missing word represents—in your head, and you talk around it,” Frame says. For example, if the target is “lilac,” it may help to describe its group, which would be plants; then, its physical qualities, such as its purple color and strong scent; and, finally, its location, such as a garden, she explains. “If you can seamlessly describe it in conversation, either you will get the word eventually or your conversation partner will.”

It’s impossible to predict whether someone will develop Long COVID and/or brain fog. Long COVID occurs more often in people whose COVID illness was severe, those who had underlying health conditions before their infections, and people who are unvaccinated, according to the CDC. But people with mild infections have had Long COVID symptoms as well, and Dr. McAlpine has had otherwise healthy patients in their 20s and 30s who’ve experienced brain fog.

If you have brain fog, it’s important to get treatment, says Frame. While everyone is different, both Frame and Dr. McAlpine say treatment and support can help in many cases.