Is Your Brain Fog a Sign of Aging, Sleep Deprivation, Long Covid or Something Else?

When Melissa Simpson got COVID last January, it began with a mild infection. “I’ve had worse flus,” she says. “But then it morphed a bit, and I was like, This isn’t going away.”

The 46-year-old Edmonton resident developed long COVID, with fatigue and persistent brain fog. She felt short of breath and tired—a simple activity like loading the dishwasher would exhaust her. And she had frustrating cognitive symptoms. “I noticed very quickly that my brain wasn’t firing. I was like, Wow, I’m not myself,” says Simpson.

She started stuttering and stumbling over her words, and she would forget what a friend had told her the day before. She couldn’t remember the way to familiar places and had trouble driving her car. “I drive a manual, and the gearshift was very confusing,” she explains. She felt like it wasn’t safe for her to drive anymore. “It was unnerving.”

Simpson was too sick to return to her job as a safety professional in the oil sands in Fort McMurray, so she took time off work and devoted herself to getting better. She saw a string of health-care professionals, including a family doctor, occupational therapists, physiotherapists, an exercise therapist, a psychologist and long-COVID specialists that included a cardiologist and a neurologist. They gave her several standardized tests, including an in-clinic questionnaire that assessed her cognitive state.

She found the occupational therapy most helpful for her brain fog. Initially, the therapy was mostly memory exercises, and Simpson says it was frustrating and headache-inducing. So instead, the occupational therapist focused on strategies to help Simpson manage her fatigue, since her cognitive issues get worse when she’s tired. These include taking it easy: Running one errand a day, for example, might be all she can handle.

Simpson has started to feel slightly better over time, especially when she schedules her days correctly. But she’s still far from her old self and she hasn’t returned to work. “Before COVID, I was contemplating going back to school for a Master’s degree while also working full time, and now I can’t remember what day of the week it is—so that may not be my best choice,” she says, laughing. Juggling both now seems impossible to her.

She’s better at recalling her pre-COVID life than processing or retaining new information. Now, she says, “I’m trying to remember, Did I feed the dog? Did I let the dog in? Did I take my medication? I feel like I’m 85. People say to me, ‘Oh, you’re just getting old,’ and I’m like, ‘No, I got old in a day.’”

Simpson’s symptoms—issues with focus, memory, processing speed, attention and multitasking—are common in long COVID cases. But long COVID isn’t the only cause of what’s formally known as cognitive dysfunction, and more commonly understood as brain fog.

Brain fog can co-occur with depression and anxiety. It can appear during menopause and chemotherapy. It can follow a concussion or arise during pregnancy and postpartum, when it’s given the disparaging (and annoying) moniker “mommy brain.”

We have all misplaced our phone or forgotten the name of an acquaintance we’ve run into on the street, but brain fog can differ in magnitude. People with brain fog feel “off.” They find they can’t concentrate at work, have trouble multitasking or can’t focus for long enough to read.

We do know the mechanisms and biological processes behind some of brain fog’s causes. “Chemo brain,” for example, can be caused by toxic chemicals that are part of cancer treatment, or by steroids, anti-nausea drugs and pain medication. The memory issues that many people experience during menopause are likely the result of a drop in estrogen. But for many other sufferers, brain fog remains a medical mystery. And that can leave people wondering if they have ADHD or early-onset Alzheimer’s—or something else entirely, compounding the distress they already feel.

Doctors can use standardized tests such as the Montreal Cognitive Assessment, which uses a series of drawing exercises, picture identification, math problems and memory recall prompts to evaluate cognitive abilities. But more commonly they’ll simply discuss the symptoms that patients have noticed (it’s a good idea to keep a list). That’s because even people who report feeling very frustrated, and even disabled, by their new difficulties can, nonetheless, score within the normal range of cognitive abilities.

We’re still learning about what exactly causes brain fog and why it can afflict some of us and not others. But new research is shedding light on when it might subside—and how to manage or limit its impact.

Long Covid Brain Fog

Alexandra Rendely, a physical medicine and rehabilitation doctor with Toronto Rehab’s Post-COVID Condition Rehab Clinic, says that brain fog is one of the top five reasons people visit the clinic to seek help. “When it comes to brain fog, we’ve seen everything from some mild word-finding difficulties to patients who were previously very high-functioning and had not yet returned to work,” she says. Many patients at the clinic have had friends and even doctors suggest that their symptoms are all in their head, so to speak, and are grateful to just have their concerns taken seriously. “Validating that you understand that they are not back to the person they were…patients are very appreciative,” she says.

Three years into the pandemic, doctors and patients now have much more information about long COVID. We have a sense of how common it is (in 2022, Statistics Canada reported that nearly 15 percent of people who got COVID still had symptoms three months later), whether it also affects people who had mild cases (yes) and its dominant symptoms: fatigue, cough, shortness of breath and brain fog, which about 33 percent of people with long COVID said they experienced. Soon, we might even have a way to help prevent it. A study published in The Lancet Infectious Diseases journal found people who took the common diabetes drug metformin shortly after getting COVID were 41 percent less likely to develop long COVID.

That’s comforting news for people who’ve yet to contract long COVID, but more help is needed for people suffering now. When it comes to long COVID’s impact, the extent of cognitive issues varies from person to person, says Angela Cheung, a professor of medicine at the University of Toronto and a senior physician scientist at Toronto General Hospital Research Institute. “Some people are functioning with minor memory issues—Oh, I forgot where I put my keys or my glasses—and then there are people who can’t read,” she explains. Often, these issues go hand-in-hand with symptoms of fatigue, as exhaustion diminishes brain function.

Exactly how COVID causes brain fog is unclear, but researchers have a few theories. People who have been hospitalized in intensive care units with severe forms of the disease might see their oxygen levels drop low enough to lead to a brain injury. In fact, anyone who is in intensive care can have cognitive issues when they come out—it’s known as post-intensive care syndrome. (Doctors need to give medications to patients before putting them on a ventilator, and some of those medications can also be neurotoxic.)

But even those who only had mild COVID symptoms, like Simpson, can develop cognitive issues. That might be because they have an extreme immune response or inflammation in the brain during and after their COVID infection.

There is no cure for long COVID yet, though studies like the new RECLAIM trial (a Canada-wide randomized trial comparing the effectiveness of treatments for long COVID-19) are searching for drugs that might reverse it. In the meantime, treatments for brain fog and long COVID primarily work on the other issues connected to it, like sleep problems and mood disorders, as well as teaching patients how to pace themselves, says Rendely.

Getting enough sleep is vital because it increases energy levels and boosts mood, which can impact memory, Rendely adds. Her clinic also recommends limiting alcohol—“That’s very beneficial for cognitive function,” she says—as well as eating a healthy diet and maintaining social interactions. And treating co-occurring conditions, such as anxiety and depression, can also help.

Cheung says that her team does not tend to recommend daily exercise to patients, however, because for many long COVID sufferers, symptoms can flare up after working out. Even walking down the street can be too much for some. “We don’t totally understand the mechanism, but what we do see is that those who keep yoyoing between flare-ups will find it harder to recover,” Cheung explains.

Brain Fog & Mental Health

Though we often think of depression and anxiety as conditions that make people feel sad or worried, they can cause brain fog as well. People with depression can find it hard to concentrate or make decisions. And people with anxiety can also have working memory issues—like struggling to remember what they want to say in a conversation.

With these diseases, neurotransmitters like serotonin and dopamine are affected. “Without the proper activity of the dopamine and serotonin in our brains, we could end up having slow thoughts, problems with memory and concentration, low energy and impaired sleep,” explains Michael Mak, a psychiatrist and sleep medicine specialist at Toronto’s Centre for Addiction and Mental Health.

Mak says that this can turn into difficulty with completing tasks or performance issues at work. Fortunately, treating the underlying mental health issue can potentially resolve these brain problems. The first step, he says, is to see your doctor and talk to them about how you’re feeling, so they can identify if you have depression, anxiety or a different issue.

Brain Fog & Menopause

According to a 2020 study published in JAMA, nearly two-thirds of women report memory problems during menopause. Common complaints include trouble remembering words and numbers, difficulty concentrating, being easily distracted and forgetting appointments and other events. Though these problems are very real, most women can still function and work normally despite them.

Women are particularly susceptible to cognitive issues in the four to eight years before, and the year after, their final period, says Alison Shea, a menopause specialist, OBGYN and assistant professor at McMaster University in Hamilton, Ont. That final menstrual cycle is often around age 50, but can happen as early as 40. She says many women are initially confused about what’s happening to them and are surprised to realize that their forgetfulness is connected to hormonal changes.

Thankfully, says Iliana Lega, an endocrinologist at Women’s College Hospital and assistant professor at the University of Toronto, this is starting to change as “brain fog becomes increasingly recognized in menopause.” Experts theorize that the brain fog is tied to drops in estrogen, but it’s an area of study that needs more research.

Another part of the cognitive fuzziness women experience is due to the fact that menopause can cause a host of other symptoms. Night sweats disrupt sleep, and studies show that sleep disturbance leads to issues with problem solving and memory. About 30 percent of women going through menopause also have depression, according to a 2015 study published in Women’s Midlife Health. Many others have anxiety, which can also cause cognitive issues and interrupt sleep.

It’s unclear whether hormone replacement therapy (HRT) can help alleviate brain fog directly. “The types of studies we need just haven’t happened,” explains Lega. A few studies that looked at the effects of HRT on cognitive function found that it didn’t show significant improvement. But for some women, it can be a safe option to try. Treating other menopause-related conditions, such as sleep and mood disorders like anxiety and depression, can also help.

Doing aerobic exercise, eating more vegetables and managing hypertension, diabetes and arteriosclerosis can all ease brain-fog symptoms, according to guidelines released in 2021 by the Society of Obstetricians and Gynaecologists of Canada. If a woman comes in complaining about their memory, says Shea, it’s wise to check for high blood sugar, hypertension or high cholesterol, as these underlying health conditions can exacerbate memory problems.

Brain Fog & Chemotherapy

There is a technical term for what’s often referred to as “chemo brain:” it’s cancer-related cognitive impairment, or chemotherapy-induced cognitive impairment. In most people, “chemo brain” subsides within the year following treatment, but some people feel its effects for longer. MRI brain scans in breast cancer patients have found an increased likelihood of less grey matter and white matter in their brains after their treatments—changes correlated with neurocognitive deficits. Some patients say they can’t multitask or focus enough to read a book. Memory, processing speed and concentration are usually affected. Some researchers believe that chemotherapy, in essence, speeds up the aging of your brain, with inflammation, toxic medication and damage to a type of cell—called a progenitor cell, in the central nervous system—all contributing to the issue.

There isn’t strong evidence around how to improve cognitive dysfunction after chemotherapy, but some cancer centres are offering cognitive rehabilitation to help patients cope with both their brain fog and their distress around cancer. Strategies include physical exercise, relaxation and mindfulness training and cognitive rehabilitation therapy with speech therapists and neuropsychologists. There are also computer-based brain-training programs and biofeedback sessions, which are a form of alternative mind-body therapy that use electrical sensors to help people monitor and learn to control their breathing, heart rate and brain activity.

Postpartum Brain Fog

Up to 80 percent of new moms say they have cognitive issues during pregnancy, like being forgetful and feeling “foggy,” and it often continues after delivery thanks to the substantial postpartum hormonal shifts. In fact, these symptoms can last up to six years after having a baby. The added stress and sleepless nights that come with pregnancy and raising little kids can also affect memory, as do postpartum depression and postpartum anxiety.

MRI scans have revealed that grey matter shrinks in some brain areas and increases in others after pregnancy. But there is good news: The brain seems to bounce back by middle age, when studies have found that women who have given birth generally have better memory recall than those who haven’t.

Researchers are also pushing for a reframing of these so-called problems. In an article in JAMA Neurology called “It’s Time to Rebrand Mommy Brain,” researchers argued: “Our long-held negative narrative of ‘mommy brain’ does not tell the full story of how the brain functions with motherhood.” The stereotypical depiction of mommy brain focuses our attention on what we lose, while ignoring what’s gained, they argue.

When the researchers tested memory in pregnant women using infant-related items such as highchairs, bibs, toys and baby clothes, they found they were better at learning about them than women who had never been pregnant—suggesting the issue might be one of focus rather than an across-the-board decline. And objective differences have rarely been observed, with only small, subjective reports of decreased cognitive function.

Postpartum, the differences are even slighter, with no significant disparities in the recall abilities of mothers versus non-mothers. So how does that square with many mothers’ experiences of feeling foggy? It might be that taking a mom out of her home or busy life into a quiet, calm lab changes her cognitive state—but it’s in the chaos of real life that she feels like her brain is not up to the task, the researchers suggest. Or, mothers might be primed to remember or self-criticize their mental lapses. They discount or ignore all that they’re learning in new parenthood while worrying about the “mommy brain” they’ve heard about.

Another key point to remember is that brain changes aren’t necessarily harmful. They’re a sign of neuroplasticity—of immense change in a period of life when women need to learn quickly about their infants, juggle new demands and regulate their own turbulent emotions, all on very little sleep.

Brain Fog & Concussions

People recovering from concussions can have challenges with recall, memory and attention. Often, their problems are worse at the end of the day, and they can have trouble concentrating, even for short periods of time, or they report feeling cognitively slower. They may have difficulty with their working memory, or struggle to learn and retain new information and with remembering things in general.

“Brain fog comes up quite often as a concussion symptom,” says Charles Tator, a neurosurgeon and director of the Canadian Concussion Centre, which is part of University Health Network’s Krembil Brain Institute in Toronto. It affects not just memory but also executive functioning and the ability to multi-task. “People tell me that they may be able to handle one or two tasks [at work], but then the telephone rings and they have to go to something else. Then their memory can’t catch up. Or for people who can handle many things at once and make five decisions—What am I going to eat, what am I going to wear, how am I going to get to the office?—they feel overloaded. You can’t make decisions, you can’t remember the day of the week, you’re foggy.”

Those symptoms could last just a few days, but in some cases they can become permanent. “We have people who never go back to baseline,” Tator says.

Medical history—how many concussions a patient has suffered, cumulatively—matters a lot. Three-quarters of people will recover from their first concussion in about a month, but each subsequent one takes longer. And the force of the injury is a critical factor, too. Concussions from car crashes are generally much harder to recover from than those incurred during sports.

While doctors can help address the anxiety, depression and vertigo stemming from concussions, there isn’t a treatment for the memory and recall issues that go with it. “The treatment for concussion is still very rudimentary,” says Tator. “We don’t even have an exact explanation of where in the brain the problem is.” He adds that symptoms might be a result of inflammation or of brain degeneration from chronic traumatic encephalopathy, a disease that’s caused by repeated brain trauma. “We’re still trying to solve these mysteries.”

For recovery strategies, Tator recommends that patients work on their sleep hygiene (making sure to go to sleep and wake up at the same time every day, for example, and reducing caffeine), along with seeking out a sleep study to rule out sleep apnea. Limiting alcohol consumption to no more than one drink a day, and never drinking all seven days of the week, also tends to improve cognitive function.

Working out—even something as simple as a daily walk—also improves sleep and produces growth factors in the brain. But patients should be sure to stay in their “window of tolerance,” says Tator. Pushing too hard can actually worsen cognitive symptoms and slow long-term recovery. Treating anxiety and depression can also help clear the fog.

Finally, occupational therapists can help people with cognitive issues—no matter the cause—by working with them to improve their memory and response time. They can also help them develop coping skills, such as bringing a support person to medical appointments and using a calendar or writing to-do lists at the beginning of the day when they have more energy.

A patient’s brain fog might not fully lift, says rehabilitation doctor Alexandra Renderly. “But we can still help them get back to doing the activities they enjoy.”

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