‘I have a hard time remembering things.’ What is brain fog and how can I treat it?

Research shows it can affect people for months and take over many aspects of life

Q: I have a hard time remembering things and often feel exhausted, like I can’t clear my head at all. Is this brain fog and is there anything I can do to fix it?

A: The blank space in your mind, when it appears, can be confusing. What were you just saying? Did you need to pick up chicken and carrots on your way home, or was it just the chicken? Why is it suddenly so hard to pay attention to what you’re doing, and why does it feel like your brain is suddenly 30 years older than you are?

If you’re feeling sluggish and forgetful, easily distracted or completely overwhelmed by mundane tasks, you may be experiencing a common phenomenon known as brain fog. Although it isn’t an official clinical diagnosis that would end up in a medical chart, brain fog can arise after several sleepless nights, while taking certain medications like antihistamines, or as a result of jet lag — among many other scenarios. Some people experience a form of brain fog after indulging in a big meal, during particularly stressful periods of life, or when undergoing big hormonal changes, such as during pregnancy or menopause.

Brain fog can also be a symptom of illness; it can occur with Lyme disease, lupus and multiple sclerosis, after cancer treatment or even during a particularly bad cold.


In recent years, the term has also become closely associated with the cognitive impairment many people experience during or after a bout with Covid-19. Roughly 20 per cent to 30 per cent of Covid-19 patients have some brain fog that persists or develops during the three months after their initial infection, and more than 65 per cent of those with long Covid report neurological symptoms too. “It’s becoming a neurological health crisis,” says Dr Michelle Monje, a neurologist at Stanford University who has studied both chemotherapy- and coronavirus-related cognitive impairment.

Q: When should you see a doctor?

Brain fog can be frustrating and worrisome no matter when or how you get it. The cognitive issues may wax and wane — in Covid-19-related brain fog as well as other types, says Jacqueline Becker, a clinical neuropsychologist at Mount Sinai Hospital in New York. But if your symptoms persist over several weeks or make life agonisingly difficult, you should seek a medical evaluation.

Brain fog can present in so many different ways and because it has so many different causes, the diagnostic tests have their limitations

“There are some people who are able to carry on with their jobs and their regular lives, but they may need to take more frequent breaks between tasks,” Becker says. “And then there are other people who are just completely disabled by this.”

How is it diagnosed?

Although brain fog sounds vague and temporary, like bad weather that will clear over time, research is beginning to show that it can affect some people for months and take over many aspects of life, compared with run-of-the-mill sluggishness or forgetfulness. Brain fog tends to affect executive function — a set of skills that are essential for planning, organising information, following directions and multitasking, among other things. “When executive function is impaired, it will often impact several domains of cognitive ability,” Becker says.

Many clinicians prefer to use the term “cognitive impairment” to lend more medical legitimacy to what patients go through, and start the diagnostic process with cognitive exams used to measure executive function in severe illnesses such as dementia, Becker says. The key difference is that brain fog does not get progressively worse the way mental abilities degenerate with dementia. You may have some days that are worse than others, but brain fog tends to impair your cognitive function to the same extent each time.

A variety of blood tests can also help point to some causes of cognitive impairment, such as sleep apnoea, vitamin B deficiency, or other hormone and thyroid issues, says Dr. Joanna Hellmuth, a neurologist at the University of California, San Francisco. But because brain fog can present in so many different ways and because it has so many different causes, the diagnostic tests have their limitations, she says.

Sometimes brain fog may be hard to diagnose because it is caused by several different factors, even for a patient who has one overarching condition. Someone with lupus or multiple sclerosis, for example, may experience cognitive impairment because of direct damage to their brain cells — but they also may not be getting enough sleep, could have extensive fatigue or be on medications that contribute to brain fog.

Unlike with lupus and multiple sclerosis, direct damage to brain cells is much rarer in Covid-19. But some patients’ brains show dysregulation in their endothelial cells, which line blood vessels in the brain. This can lead to a more permeable blood-brain barrier that allows harmful substances through to the brain and changes cognitive function, Hellmuth says.

Physical activity can help improve your ability to focus, as well as increase neural connectivity and memory formation in the brain

Researchers are finding that a more common cause of brain fog in Covid-19 patients, as well as those who have been infected with other viruses such as HIV and Ebola, and even people who undergo chemotherapy for cancer, is inflammation — a steep and unwarranted increase in immune-cell activity that can wreak havoc — in the brain and the body. Studies show that patients with persistent cognitive impairment after Covid-19 have high levels of inflammatory markers in their blood and cerebrospinal fluid. “We’re just seeing a new virus creating the same old problem,” says Dr. Avindra Nath, clinical director at the National Institute of Neurological Disorders and Stroke.

Q: How do you clear up brain fog?

Even if doctors can’t find a physical cause for your brain fog, there are steps you can take to manage it, Hellmuth says. Start with short-term adaptive strategies to manage everyday tasks. Write notes and set alarms so that you don’t miss appointments. Take regular breaks during long projects so you’re better able to maintain focus and finish tasks. You might also try tracking your daily activities, using an app on your phone or just a notebook to figure out what times of day you feel most energetic and clearheaded. Then, reserve this time to do more difficult or complicated tasks.

Your healthcare provider may also suggest making lifestyle changes to improve your overall health and energy. “We try to encourage cardiovascular exercise, a good diet, sleep and social activities that are known to be beneficial for the brain,” Hellmuth says.

Physical activity can help improve your ability to focus, as well as increase neural connectivity and memory formation in the brain. If you don’t feel up for rigorous workouts, try doing them in small chunks so you can slowly build up your aerobic fitness. Make sure you stay hydrated and eat a variety of foods high in vitamins and antioxidants. And reach out to friends and family for support. Studies have shown that maintaining a rich social network not only helps reduce stress during difficult times, it can also enhance intellectual stimulation and improve your brain health.

You’ll also want to get better rest, which, of course, is easier said than done for patients with long Covid, those who are undergoing chemotherapy or experiencing life changes such as pregnancy or menopause. Take measures to relax your mind at night. Unplug your electronics and create a restful environment. — This article originally appeared in The New York Times